Printronix P7000 User Manual page 301

Signals
Host Clock / nWrite. Driven by host. Data transferred from host to
printer. When printer sends data, two types are available. If Nibble
mode, signal is set high. If Byte mode, signal is set low.
Data 1 through Data 8. These pins are host-driven in Compatibility
mode and bidirectional in Byte mode. They are not used in Nibble
mode. Data 1 is the least significant bit; Data 8 is the most significant
bit.
Printer Clock / Peripheral Clock / Interrup. Driven by the printer. A
signal from the printer indicating the character or function code has
been received and the printer is ready for the next data transfer.
Printer Busy / Peripheral Acknowledge / nWait. Driven by the
printer. Indicates the printer cannot receive data. (Data bits 4 and 8 in
Nibble mode.)
Acknowledge Data Request / nAcknowledge Reverse. Driven by the
printer. Indicates the printer is in a fault condition. (Data bits 3 and 7 in
Nibble mode.)
Xflag. Driven by the printer. A high true level indicating the printer is
ready for data transfer and the printer is on line. (Data bits 2 and 6 in
Nibble mode.)
Host Busy / Host Acknowledge / NDStrobe. Driven by the host.
Activates auto-line feed mode.
Peripheral Logic High. Driven by the printer. When the line is high, the
printer indicates all of its signals are in a valid state. When the line is
low, the printer indicates its power is off or its signals are in an invalid
state.
nReverse Request. Driven by the host. Resets the interface and forces
a return to Compatibility mode idle phase.
nData Available / nPeripheral Request. Driven by the printer.
Indicates the printer has encountered an error. (Data bits 1 and 5 in
Nibble mode.)
1284 Active / nAStrobe. Driven by the host. A peripheral device is
selected.
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