10. Commands for Printer Devices 10.1. Model for Printer Devices This command set includes capability for the printer-controlling device, which is an SCSI target to be is functionally separate from the physical printer device (see Figure 10-1) as well as integrated with it. The physical printer device is connected to the SCSI target via one of several common device-level interfaces. There may be more than one physical printer device attached to the printer controlling device. In such a case, each physical printer device is assigned a separate logical unit number, beginning with zero. The printer-controlling device, printer device-level interface, and the physical printer device are collectively referred to as the printer device. --------------- ------------ | | | | ----------| Printer- | Printer Device- | Physical | SCSI Bus | Controlling |-----------------| Printer | ----------| Device | level Interface | Device | | | | | --------------- ------------ Figure 10-1: SCSI Printer Model Specific control mechanisms are defined in mode pages for two industry- standard interfaces known as the line printer interface (e.g., the Data Products interface or equivalent) and the EIA RS-232C interface. These mode pages are used to control optional features of these interfaces. No mode page was defined for the popular industry-standard parallel interface because the options requiring controls are embedded in the data. The printer-controlling device may be physically integrated within the printer device and it is not required to use one of the industry-standard interfaces referenced above. The printer device commands are structured on the assumption that specific printer control codes may be embedded in the data transferred by the FORMAT, PRINT, and SLEW AND PRINT commands. The transparent control codes may take the form of "escape code sequences". Commands for the operation of the target function and some printer controls, which are not convenient to handle in a transparent way, are specified in 10.2. This standard does not specify which character set is used by the printer device nor does it specify the meaning of the "escape code sequences" that may be used. 10.2. Commands for Printer Devices The commands for printer devices shall be as shown in Table 10-1. Table 10-1: Commands for Printer Devices ============================================================================== Operation Command Name Code Type Section Page ------------------------------------------------------------------------------ CHANGE DEFINITION 40h O 7.2.1 COMPARE 39h O 7.2.2 COPY 18h O 7.2.3 COPY AND VERIFY 3Ah O 7.2.4 FORMAT 04h O 10.2.1 INQUIRY 12h M 7.2.5 LOG SELECT 4Ch O 7.2.6 LOG SENSE 4Dh O 7.2.7 MODE SELECT(6) 15h O 7.2.8 MODE SELECT(10) 55h O 7.2.9 MODE SENSE(6) 1Ah O 7.2.10 MODE SENSE(10) 5Ah O 7.2.11 PRINT 0Ah M 10.2.2 READ BUFFER 3Ch O 7.2.12 RECEIVE DIAGNOSTIC RESULTS 1Ch O 7.2.13 RECOVER BUFFERED DATA 14h O 10.2.3 RELEASE UNIT 17h M 9.2.9 REQUEST SENSE 03h M 7.2.14 RESERVE UNIT 16h M 9.2.10 SEND DIAGNOSTIC 1Dh M 7.2.15 SLEW AND PRINT 0Bh O 10.2.4 STOP PRINT 1Bh O 10.2.5 SYNCHRONIZE BUFFER 10h O 10.2.6 TEST UNIT READY 00h M 7.2.16 WRITE BUFFER 3Bh O 7.2.17 ============================================================================== Key: M = Command implementation is mandatory. O = Command implementation is optional. The following operation codes are vendor specific: 01h, 02h, 05h, 06h, 07h, 08h, 09h, 0Ch, 0Dh, 0Eh, 0Fh, 11h, 13h, 19h, and C0h through FFh. All remaining operation codes for printer devices are reserved for future standardization. 10.2.1. FORMAT Command Table 10-2: FORMAT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (04h) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Format Type | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | Transfer Length | -----|--- ---| 4 | (LSB) | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The FORMAT command (Table 10-2) provides a means for the initiator to specify forms or fonts to printers that support programmable forms or fonts. The format information is peripheral-device specific. The format type field specifies the type of format information to be transferred from the initiator to the target. This field is defined as follows: DB(1) DB(0) Format Type ----- ----- ------------- 0 0 Set Form 0 1 Set Font 1 0 Vendor Unique 1 1 Reserved The transfer length specifies the length in bytes of format information that shall be transferred during the DATA OUT phase. A transfer length of zero indicates that no format information shall be transferred. This condition shall not be considered as an error. 10.2.2. PRINT Command Table 10-3: PRINT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (0Ah) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | Transfer Length | -----|--- ---| 4 | (LSB) | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The PRINT command (Table 10-3) transfers the specified number of bytes from the initiator to the target to be printed. The transfer length specifies the length in bytes of data that shall be transferred during the DATA OUT phase. A transfer length of zero indicates that no data shall be transferred. This condition shall not be considered as an error. 10.2.3. RECOVER BUFFERED DATA Command Table 10-4: RECOVER BUFFERED DATA Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (14h) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | Transfer Length | -----|--- ---| 4 | (LSB) | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The RECOVER BUFFERED DATA command (Table 10-4) returns to the initiator data that has been previously transferred to the target, but not yet printed. This command is normally used only to recover from error or exception conditions that make it impossible to print the buffered data. The order in which data are transferred from the target to the initiator is the same as when the data were previously transferred using the PRINT command or SLEW AND PRINT command. Data transferred by this command are deleted from the target data buffer. One or more RECOVER BUFFERED DATA commands may be used to return the buffered data that is not printed. If an attempt is made to recover more data than is contained in the buffer, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to NO SENSE. In addition, the EOM, valid, and ILI bits shall be set to one. The information bytes shall be set to the difference (residue) between the transfer length and the actual number of bytes returned. The transfer length specifies the maximum length in bytes of data that shall be transferred during the DATA IN phase. A transfer length of zero indicates that no data shall be transferred. This condition shall not be considered as an error. 10.2.4. SLEW AND PRINT Command Table 10-5: SLEW AND PRINT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (0Bh) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Channel| -----|-----------------------------------------------------------------------| 2 | Slew Value | -----|-----------------------------------------------------------------------| 3 | (MSB) | -----|--- Transfer Length ---| 4 | (LSB) | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The SLEW AND PRINT command (Table 10-5) transfers the specified number of bytes from the initiator to the target to be printed. This command is provided for printer devices that do not support forms control information embedded within the print data. The transfer length specifies the length in bytes of data that shall be transferred during the DATA OUT phase. A transfer length of zero indicates that no data shall be transferred. This condition shall not be considered as an error. If the channel bit is zero, the slew value specifies the number of lines the form shall be advanced before printing. A value of 255 indicates that the form shall be advanced to the first line of the next form before printing. If the channel bit is one, the slew value specifies the forms control channel number to which the form shall be advanced prior to printing the data. If implemented, the printer options page in the MODE SELECT command provides additional control over the usage of the slew value field. If the channel bit is one, and the channel option is not implemented, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. 10.2.5. STOP PRINT Command Table 10-6: STOP PRINT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (1Bh) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Retain | -----|-----------------------------------------------------------------------| 2 | Vendor Unique | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The STOP PRINT command (Table 10-6) requests the target to halt printing on buffered devices in an orderly fashion. A retain bit of zero requests that the target data buffer be discarded; otherwise, the data not printed shall be retained. The data not printed may be recovered using the RECOVER BUFFERED DATA command, if implemented by the target. A subsequent SYNCHRONIZE BUFFER command, PRINT command or SLEW AND PRINT command shall cause the remaining data not already printed and to be printed followed by the data transferred by the subsequent command, if any. The point at which printing is suspended by this command is vendor specific. 10.2.6. SYNCHRONIZE BUFFER Command Table 10-7: SYNCHRONIZE BUFFER Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code (10h) | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Control | ============================================================================== The SYNCHRONIZE BUFFER command (Table 10-7) provides a means for an initiator to ensure that the data have been successfully printed prior to releasing the peripheral device. This is useful for applications that wish to handle any error or exception conditions (e.g., end-of-medium) prior to termination of the application. When all buffered data are actually printed the command shall be terminated with a GOOD status. If it is not possible to finish printing all of the buffered data (due to an error or exception condition on the peripheral device), then this command shall be terminated with a CHECK CONDITION status and the appropriate sense key. The printer options page in the MODE SELECT command, if implemented, provides additional control over termination sequences when using this command. 10.3. Parameters for Printer Devices 10.3.1. Diagnostic Parameters This section defines the descriptors and pages for diagnostic parameters used with printer devices. The diagnostic page codes for printer devices are defined in Table 10-8. Table 10-8: Diagnostic Page Codes ============================================================================== Page Code Description Section ------------------------------------------------------------------------------ 00h Supported Diagnostic Pages 7.3.1.1 01h-3Fh Reserved (for all device type pages) 40h-7Fh Reserved 80h-FFh Vendor-specific pages ============================================================================== 10.3.2. Log Parameters This section defines the descriptors and pages for log parameters used with printer devices. The log page codes for printer devices are defined in Table 10-9. Table 10-9: Log Page Codes ============================================================================== Page Code Description Section ------------------------------------------------------------------------------ 01h Buffer Over-Run/Under-Run Page 7.3.2.1 07h Last n Error Events Page 7.3.2.3 06h Non-Medium Error Page 7.3.2.4 00h Supported Log Pages 7.3.2.5 02h - 05h Reserved 08h - 2Fh Reserved 3Fh Reserved 30h - 3Eh Vendor-specific pages ============================================================================== 10.3.3. Mode Parameters This section defines the descriptors and pages for mode parameters used with printer devices. The mode parameter list, including the mode parameter header and mode block descriptor are described in 7.3.3. The medium-type code field is contained in the mode parameter header (see Table 7-61 and 7-62). This field is reserved for printer devices. The device specific parameter field is contained in the mode parameter header (see Table 7-61 and 7-62). Table 10-10 defines the device specific parameter used for printer devices. Table 10-10: Printer Device Specific Parameter ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | ============================================================================== |Reserved| Buffered Mode | Reserved | ============================================================================== When using the MODE SELECT command, a buffered mode of zero indicates that the target shall not report a GOOD status on PRINT commands or SLEW AND PRINT commands until the data are actually printed. A buffered mode of one indicates that the target may report a GOOD status on PRINT commands or SLEW AND PRINT commands as soon as the data have been transferred to the SCSI device buffer. The data from one or more commands may be buffered prior to printing. Buffered modes of 2h through 7h are reserved. When using the MODE SENSE command, the buffered mode field returns the current value of this parameter. The density code field is contained in the mode parameter block descriptor (see Table 7-63). This field is reserved for printer devices. The mode page codes for printer devices are shown in Table 10-11. Table 10-11: Mode Page Codes ============================================================================== Page Code Description Section ------------------------------------------------------------------------------ 00h Vendor Specific (does not require page format) 0Ah Control Mode Page 7.3.3.1 02h Disconnect-Reconnect Page 7.3.3.2 03h Parallel Printer Interface Parameters 10.3.3.1 09h Peripheral Device Page 7.3.3.3 05h Printer Options 10.3.3.2 04h Serial Printer Interface Parameters 10.3.3.3 01h Reserved 06h - 08h Reserved 0Bh - 1Fh Reserved 20h - 3Eh Vendor Specific (page format required) 3Fh Returns all pages (valid only for the MODE SENSE command) ============================================================================== 10.3.3.1. Parallel Printer Interface Parameters Page This page (Table 10-12) is intended to support printer devices which use the industry-standard line printer interface. Table 10-12: Parallel Printer Interface Parameters ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | PS |Reserved| Page Code (03h) | -----|-----------------------------------------------------------------------| 1 | Parameter Length (03h) | -----|-----------------------------------------------------------------------| 2 | Parity Select | PIPC |Reserved| VCBP | VCBS | VES | Autofd | -----|-----------------------------------------------------------------------| 3 | Reserved | ============================================================================== The parameters savable (PS) bit is only used with the MODE SENSE command. This bit is reserved with the MODE SELECT command. A PS bit of one indicates that the target is capable of saving the page in a non-volatile vendor- specific location. The parity select field specifies parity generation on the printer interface and is defined as follows: Code Parity Select ---- ------------------------- 00b No parity generation 01b Even Parity 10b Odd Parity 11b Reserved A paper instruction parity check (PIPC) bit of one indicates that the printer interface "Paper Instruction" signal is included in parity generation on the printer interface by the target. A PIPC bit of zero indicates that the "Paper Instruction" signal is not included in parity generation on the printer interface by the target. IMPLEMENTORS NOTES: (1) The format of the vertical forms unit (VFU) control byte is specified by the VCBP, VCBS, and VES bits. The VFU control byte is not part of this standard, however a discussion of it is included here for a better understanding. This VFU control byte (see table, below) includes a control bit (C) to select whether to slew over a number of lines or to skip to a vertical forms unit (VFU) channel number. This bit may be located in two different bit positions and may have either polarity. (2) The number of lines to slew over may be coded as an unsigned four-bit number (NNNN) or an unsigned six-bit number (EENNNN). The upper two bits of the six-bit number (EE) may be positioned contiguously with the lower four bits (NNNN) or they may be separated from the lower four bits by the control bit (C). Furthermore, the upper two bits may or may not be supported. (3) The VFU channel to select is specified by an unsigned four-bit number (NNNN) in the VFU control byte. (4) Pictorially, the control byte is as follows: VFU Control Byte Description 7 6 5 4 3 2 1 0 --------------- ------------------------------------------ 0 E E C N N N N Advance (EE)NNNN lines (C = line skip) 0 0 0 C N N N N Skip to VFU channel NNNN (C = VFU channel) 0 C E E N N N N Advance (EE)NNNN lines (C = line skip) 0 C 0 0 N N N N Skip to VFU channel NNNN (C = VFU channel) Key: C is the VFU control bit. A VFU control bit polarity (VCBP) bit of one indicates that the the VFU control bit (C) is true for a VFU channel command and false for a line skip command. A VCBP bit of zero indicates the opposite polarity. A VFU control bit select (VCBS) bit of one indicates that the control bit (C) is in bit position 6 and the EE bits are in bit positions 5 and 4. A VCBS bit of zero indicates that the control bit (C) is in bit position 4 and the EE bits are in bit positions 6 and 5. A VFU extended skip (VES) bit of one indicates that the EE bits are supported for line skip operations. A VES bit of zero indicates that the EE bits are not supported. For MODE SELECT an automatic line feed (Autofd) bit of one specifies that the target assert the printer interface "Auto Line Feed" signal. An Autofd bit of zero specifies that the target negate the printer interface "Auto Line Feed" signal. For MODE SENSE the target shall return the current value of this bit. 10.3.3.2. Printer Options Page The printer options page (Table 10-13) supports control and reporting of various target functions and features. Table 10-13: Printer Options ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | PS |Reserved| Page Code (05h) | -----|-----------------------------------------------------------------------| 1 | Parameter Length (0Ah) | -----|-----------------------------------------------------------------------| 2 | EVFU | Font Identification | -----|-----------------------------------------------------------------------| 3 | Reserved | Slew Mode | Reserved | SCTE | AFC | -----|-+---------------------------------------------------------------------| 4 | (MSB) | -----|--- Maximum Line Length ---| 5 | (LSB) | -----|-----------------------------------------------------------------------| 6 | EVFU Format Start Character | -----|-----------------------------------------------------------------------| 7 | EVFU Format Stop Character | -----|-+---------------------------------------------------------------------| 8 | Line Slew options | Form Slew Options | -----|-----------------------------------------------------------------------| 9 | Data Termination Options | Reserved | -----|-----------------------------------------------------------------------| 10 | Reserved | -----|-----------------------------------------------------------------------| 11 | Reserved | ============================================================================== The parameters savable (PS) bit is only used with the MODE SENSE command. This bit is reserved with the MODE SELECT command. A PS bit of one indicates that the target is capable of saving the page in a non-volatile vendor- specific location. An electronic vertical forms unit (EVFU) bit of one indicates that a tape or electronic vertical forms unit is present in the printer device. An EVFU bit of zero indicates that the electronic vertical forms unit should not be used or that the unit is not present in the printer device. For the MODE SELECT command, the font identification field specifies which font is to be used. For the MODE SENSE command, this field identifies the currently selected font. The font identification codes are defined as follows: Code Font Identification --------- -------------------- 00h Default Font 01h - 3Fh Reserved 40h - 7Fh Vendor specific Font For the MODE SELECT command, the slew mode field controls the target's behavior when a SLEW AND PRINT command is received with a channel bit of zero (see 10.2.4). For the MODE SENSE command, this field reports the current slew mode. This slew mode is defined as follows: Code Slew Mode ---- ---------------------------------------------------------------------- 00b SLEW AND PRINT commands with a channel bit of zero are supported without any required setup. 01b SLEW AND PRINT commands with a channel bit of zero are only accepted after the initiator issues a FORMAT command with a format type of "set form" (to initialize the electronic vertical forms unit). 10b SLEW AND PRINT commands with a channel bit of zero are always accepted. The target shall use the electronic vertical forms unit if it has previously been initialized or it shall initialize the electronic vertical forms unit for line skipping by sending the EVFU start format character immediately followed by the EVFU stop format character (both are defined below) prior to executing the SLEW AND PRINT command. 11b Reserved For the MODE SELECT command, a step count truncate enable (SCTE) bit of one indicates that the target shall assume the printer truncates slew values in SLEW AND PRINT commands so that the data is printed on the first line of the next form. A SCTE bit of zero indicates that the target shall assume the printer continues to slew over forms boundaries in SLEW AND PRINT commands if the slew value exceeds the number of remaining lines on the current form. The target shall return the current value of this field in the MODE SENSE data. An ASCII forms control (AFC) bit of one indicates that the printer supports ASCII forms control characters. An AFC bit of zero indicates that the printer does not support ASCII forms control characters. The maximum line length field specifies the maximum transfer length (maximum number of bytes per line) to be accepted in the SLEW AND PRINT command. A value of 0000h in MODE SELECT specifies that the target shall use its default value. In any case, the target shall report its actual value in the MODE SENSE data (not 0000h). The EVFU format start character field specifies the character code to be used by the target to start the initialization of the electronic vertical forms unit if slew mode option 10b is selected. The EVFU format stop character field specifies the character code to be used by the target to stop the initialization of the electronic vertical forms unit if slew mode option 10b is selected. The line slew options field specifies the implementation of the line slew (using ASCII forms control characters) in the SLEW AND PRINT command. Code values in this field are defined as follows: Code Line Slew Option ----- ---------------------------------------------------------------------- 0h Not implemented. (SLEW AND PRINT commands cause CHECK CONDITION status with ILLEGAL REQUEST sense key.) 1h The target shall insert an ASCII carriage return character (0Dh) for each line to slew over. 2h The target shall insert an ASCII line feed character (0Ah) for each line to slew over. 3h The target shall insert an ASCII carriage return character (0Dh) and line feed character (0Ah) for each line to slew over. 4h-7h Reserved 8h-Fh Vendor Unique The form slew options field specifies the implementation of form slewing in the SLEW AND PRINT command. Code values in this field are defined as follows: Code Form Slew Option ----- ---------------------------------------------------------------------- 0h Not implemented. (SLEW AND PRINT commands cause CHECK CONDITION status with ILLEGAL REQUEST sense key.) 1h The target shall insert an ASCII form feed character (0Ch) to move to the beginning of the next form. 2h The target shall insert an ASCII carriage return character (0Dh) and form feed character (0Ch) to move to the beginning of the next form. 3h-7h Reserved 8h-Fh Vendor Unique The data termination options field specifies the termination sequence to be issued to the printer device when a SYNCHRONIZE BUFFER command is received. Code values for this field are defined as follows: Code Data Termination Option ----- ----------------------- 0h Selects the target default implementation (MODE SELECT). 1h No termination sequence. (The target sends any remaining data in its buffer to the printer device with no termination sequence.) 2h The target shall print any buffered data followed by an ASCII carriage return character (0Dh). 3h The target shall print any buffered data followed by an ASCII line feed character (0Ah). 4h The target shall print any buffered data followed by an ASCII carriage return, line feed character sequence (0Dh, 0Ah). 5h The target shall send any buffered data followed by an ASCII form feed character (0Ch). 6h The target shall print any buffered data followed by an ASCII carriage return, form feed character sequence (0Dh, 0Ch). 7h The target shall issue a zero line slew command to the printer device. 8h-Bh Reserved Ch-Fh Vendor Unique 10.3.3.3. Serial Printer Interface Parameters Page This page (Table 10-14) is intended to support printer devices which use the industry-standard serial interface usually referred to as EIA RS-232C. Table 10-14: Serial Printer Interface Parameters ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | PS |Reserved| Page Code (04h) | -----|-----------------------------------------------------------------------| 1 | Parameter Length (06h) | -----|-----------------------------------------------------------------------| 2 | Reserved | Stop Bit Length | -----|-----------------------------------------------------------------------| 3 | Parity Selection |Reserved| Bits per Character | -----|-+---------------------------------------------------------------------| 4 | RTS | CTS | Reserved | Pacing Protocol | -----|-----------------------------------------------------------------------| 5 | (MSB) | -----|--- ---| 6 | Baud Rate | -----|--- ---| 7 | (LSB) | ============================================================================== The parameters savable (PS) bit is only used with the MODE SENSE command. This bit is reserved with the MODE SELECT command. A PS bit of one indicates that the target is capable of saving the page in a non-volatile vendor- specific location. The stop bit length field specifies the length of the stop bit(s) in units of 1/16 bit. The target may round this field as described in 6.5.4. A stop bit length of zero in the MODE SELECT command indicates that the target shall use its default value. The parity selection field specifies parity generation and checking as defined in the following table: Code Parity Selection ---- ---------------- 000b None 001b Mark 010b Space 011b Odd 100b Even 101b Reserved 110b Reserved 111b Reserved The bits per character field specifies the number of bits in each character. A value of zero in the MODE SELECT command indicates that the target shall use its default character size. For the MODE SELECT command, a request to send (RTS) bit of one specifies that the target shall insure the "Request to Send" (RTS) signal in the serial interface follows the line state of the "Data Terminal Ready" (DTR) signal in the serial interface. A RTS bit of zero specifies that the target shall set the "Request to Send" (RTS) signal to "high" whenever the target power is on. For the MODE SENSE command, the target shall report the current value of this field. For the MODE SELECT command, a clear to send (CTS) bit of one specifies that the target shall delay data transmission to the printer device until the printer device asserts the "Clear to Send" (CTS) signal in the serial interface. A CTS bit of zero indicates that the target shall ignore the "Clear to Send" signal. For the MODE SENSE command, the target shall report the current value of this field. The code values for the pacing protocol field are defined as follows: Code Pacing Protocol ---- --------------- 0h None 1h XON/XOFF 2h ETX/ACK 3h DTR 4h-7h Reserved 8h-Fh Vendor specific The baud rate field specifies the baud rate in bits per second. The target may round this value as described in 6.5.4. A baud rate of zero in the MODE SELECT command specifies that the target shall use its default baud rate. (This page is intentionally blank.)