Canon Color Bubble Jet BJC-2000 Series, Service Manual

Page: 43 / 136

Nibble mode
In nibble mode, the printer transfers data twice to the host computer in 4-bit units.
The data is transferred with the PtrClk signal and HostBusy signal handshakes.
After the printer confirms that the HostBusy signal is Low, it prepares 8-bit data,
lowers the PtrClk signal and outputs the lower 4-bits along the control signal line.
After the PtrClk signal is Low, the host computer receives the data and raises the
HostBusy signal. Next, after the printer confirms that the HostBusy signal is Low for
a second time, it outputs the upper 4-bits along the control signal line. If there is no
data to be sent to the host computer after the HostBusy signal is High, the DataAvail
signal becomes High and the printer stands by for the next data transfer.
Part 2: Product Specifications BJC-2000
2-19
BJC-2000
Printer Busy Status
0000 0000
Ptr
→
Host
Bit0 Bit4
Bit1 Bit5
Bit3 Bit7
Bit2 Bit6
1284 Active
Ack Data Req
Data (1 to 8)
Host Busy
Host Clk
Ptr Clk
Ptr Busy
Data Avail
Xflag
TP TP TP
Unknown
With data
Nibble mode
Support
Figure 2-11 Timing Chart (Nibble Mode)