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Print Engine Interface
MOTOROLA
MC68322 USER’S MANUAL
10-13
Figure 10-8. Command Operation—Print Engine Supplies CCLK
10.3.3 Status Operation
CCLK status information is sent to the MC68322 from the print engine. During the status
operation, serial data is assembled into the PCOMR’s printer status field. Status information
can be supplied to the MC68322 on either the STS or CMD/STS signals. If status
information is driven on STS, the CMD/STS signal will be in a high impedance state. CBSY
is in a high impedance state during the status operation.
10.3.3.1 CCLK SUPPLIED BY MC68322. In this mode, the MC68322 print engine
interface generates eight high to low transitions of CCLK so that the status data can be
sampled at every rising edge. The PICR’s CCLK divisor field must be programmed to
provide sufficient setup and hold time for the status data to be sampled.
After all eight bits of the status are sampled, the print engine interface enters a recovery
cycle. The recovery time is one half CCLK period as programmed in the PCOMR’s CCLK
divisor field. During the recovery time, SBSY is not sampled and if a command operation is
initiated it will be latched and executed after the recovery. When the status operation is
complete, the PCIER’s STR bit is set, thus indicating that the PCOMR’s printer status field
is full. If enabled, this bit can and will cause an interrupt event.
SBSY is an asynchronous signal to the print engine interface and is internally synchronized
to CLK1. The print engine should not assert the signal at any time during a command
operation or recovery cycle. Once SBSY has been asserted, it must remain that way until
the status operation is initiated. Figure 10-9 illustrates the timing diagram for a status
operation when the core supplies CCLK.
CBSY
CCLK
CMD/STS
1C
3C
4C
5C
6C
7C
8C
9C
10C
2C
A
B
C
D
SBSY and STS are not sampled during command operations.
A = CMD transmitted with the first falling edge of CCLK.
B = CMD sampled by the print engine.
C = CMD/STS hold; controlled by the CCLK divisor field.
D = Recovery cycle; half CCLK period. Any print engine response
is acknowledged after recovery cycle.
NOTES: