Parallel interface signals behaviour – Compuprint 9058 Programmer Manual User Manual
Page 136
The Parallel Interface
A78408098-003
C.7
Parallel Interface Signals Behaviour
HostClk / nWrite (nStrobe)
Compatibility Mode:
Set Active low to transfer data into printer input
latch. Data is valid while nStrobe is low.
Negotiation Phase:
Set active low to transfer extendibility request
value into printer input latch. Data is valid on
the falling edge of HostClk.
Reverse Data Transfer
Phase:
Set high during Nibble Mode transfer to avoid
latching data into printer. Pulsed low during
Byte Mode transfers to acknowledge transfer of
data from the printer. The printer shall ensure
that this pulse does not transfer a new data into
the printer input latch.
AD1..AD8 (Data 1...Data 8)
Compatibility Mode:
Forward channel data.
Negotiation Phase:
Extendibility request value.
Reverse Data Transfer
Phase:
Nibble Mode:
NOT USED.
Byte Mode:
Reverse channel data.
PrtClk (nAck)
Compatibility Mode:
Pulsed low by the printer to acknowledge the
transfer of a data from the host.
Negotiation Phase:
Set low to acknowledge 1284 support, then set
high to indicate that the Xflag (Select) and data
available flags may be read.
Reverse Data Transfer
Phase:
Used in both Nibble and Byte Modes to qualify
data being sent to the host.
PrtBusy (Busy)
Compatibility Mode:
Driven high to indicate that the printer is not
ready to receive data.
Negotiation Phase:
Reflects the present state of the printer's
forward channel.
Reverse Data Transfer
Phase:
Nibble Mode:
Data bits 3 then 7, then
forward channel busy status
Byte Mode:
Forward channel busy status.
Reverse Idle phase:
Forward channel busy status.