IBM 6400i, Руководство по установке

Страница: 252 / 370

252
Chapter 5
RS-232 And RS-422 Serial Interfaces
6400-i24 and -i2s Models
NOTE: The RS-422 is optional for the 6400-i24 model.
+RXD, -RXD.Serial data stream differentially received by printer.
+TXD, -TXD.Differentially driven serial data stream for transmitting status and
control information to the host. Subject to protocol selection.
NOTE:
±
RXD and
±
TXD form signal and return paths of a differential line
signal.
RS-232 Serial Interface Protocols
DTR. (DTE Ready). The printer controls the data flow by asserting or de-
asserting this hardware signal to the host. If there is enough room in the
printer buffer, the printer will send a high signal; if the buffer is full the printer
will send a low signal. DTR tells the host if it is safe to send more data (If the
host sends data during an unsafe condition, data will be lost.
RS-232 and RS-422 Serial Interface Protocols
X-ON / X-OF. Transmit On/Transmit Off. The printer transmits an X-ON
character (hex 11) when entering the Ready mode or when the buffer is
almost empty. The printer transmits an X-OFF character (hex 13) when
entering the Not Ready mode or when the buffer is almost full.
ETX / ACK. End of Text/Acknowledge. This host controls the flow of
communication to the printer by sending a block of data and ending the block
with an End of Text (ETX) signal. When the printer receives the ETX signal, it
will acknowledge it has received the entire block of data.
ACK / NAK. Acknowledge/Negative Acknowledge. ACK mans acknowledge;
the device acknowledges it has accepted a transmission. NAK means a
negative acknowledge; the device did not receive the transmission.
Table 7. PSA3 RS-422 Serial Interface Connector Pin Assignments
Input Signals Output Signals Miscellaneous
Signal Pin Signal Pin Signal Pin
- Receive Data
(-RXD)
1 - Transmit Data
(-TXD)
3 Chassis/Signal
Ground 5
+ Receive Data
(+RXD)
6 + Transmit Data
(+TXD)
8