Nibble Mode - Canon BJC-5000 Service Manual

Part 4: Technical Reference

2.1.2 Nibble mode

In the nibble mode, the printer transfers data twice to the host computer in 4-bit
blocks. The data is transferred with the PtrClk signal and HostBusy signal
handshakes.
After the printer confirms the falling edge of the HostBusy signal, it prepares the 8-bit
data, makes the PtrClk signal go from HIGH to LOW, and outputs the lower 4 bits on
the control signal line. After the PtrClk signal goes from HIGH to LOW, the host
computer loads the data and makes the HostBusy signal go from LOW to HIGH. After
the printer confirms the falling edge of the HostBusy signal for the second time, it
outputs the higher 4 bits on the control signal line.
If there is no data to be sent to the host computer after the HostBusy signal goes from
LOW to HIGH, the printer makes the DataAvail signal go from LOW to HIGH and is
put on standby status for the next data transfer. (The falling edge indicates a LOW
and the rising edge indicates a HIGH.)
Max. 35ms
HostBusy
PtrClk
Min. 45ms
Bit0
DataAvail
Bit1
Xflag
Bit2
AckDataReq
Bit3
PtrBusy
Figure 4-8 Interface Timing (Nibble Mode)
4-8
Max. 35ms
Bit4
Bit5
Bit6
Bit7
BJC-5000