Rs-232 Serial Interface Protocols; Rs-232 And Rs-422 Serial Interface Protocols; Rs-232 And Rs-422 Serial Interface Error Handling - IBM 6400 Setup Manual

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–OFF — 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. The 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 means
acknowledge; the device acknowledges it has accepted a transmission. NAK
means a negative acknowledge; the device did not receive the transmission.
RS–232 and RS–422 Serial Interface Error Handling
NOTE: All serial errors are treated as faults that require operator
intervention.
Parity Error Handling — Parity error checking is a configuration option
selected from the operator panel.
With odd or even parity checking selected, a character with a parity error is
replaced with a question mark (?) character.
When parity checking is not selected ("NONE" on the operator panel), parity
errors are ignored and the characters are printed as received.
Framing Error Handling — Framing error checking is always in effect for
the serial interface.
Chapter 5. Printer Interfaces 5–5