Print Engine Interface
10-12
MC68322 USER’S MANUAL
MOTOROLA
A recovery cycle is then initiated, during which no command or status operations are
performed. If a subsequent command operation is initiated during this time, it will be latched
and started after the recovery. If SBSY becomes active, indicating a status operation, then
it must remain active until the end of the recovery, which has the duration of one half CCLK
period. Figure 10-7 illustrates the timing diagram for a command operation when the core
supplies CCLK.
Figure 10-7. Command Operation—MC68322 Supplies CCLK
10.3.2.2 CCLK SUPPLIED BY PRINT ENGINE. In this mode, the print engine interface
expects eight rising edge transitions of CCLK from the print engine. Because CCLK is
asynchronous to CLK1, it is synchronized inside the MC68322. As a result, the period of this
signal can be no less than four CLK1 periods. When a command operation is initiated, CBSY
transitions to an active state and stays active until all command bits are transferred and hold
time (the value in the PCOMR’s CCLK divisor field) for the last command bit is satisfied.
Command data is transferred on CMD/STS, which remains in high impedance until the first
falling edge of CCLK. The command bit changes three CLK1 periods after every falling edge
of the CCLK. At the end of the transmission, CMD/STS is brought high for one CLK1 period
and then returns to the high impedance state. When CBSY transitions to an inactive state
(indicating the end of the command operation), the PCIER’s CMS bit is set to notify the core
that the command has been sent, thus causing a command sent interrupt event to occur.
The software should not try to write another command until this interrupt is received.
SBSY and STS, which are used during status operations, should not be asserted during a
command operation. Figure 10-8 illustrates the timing diagram for a command operation
when the print engine supplies CCLK.
CBSY
CMD/STS
1C
3C
4C
5C
6C
7C
8C
9C
10C
2C
A
B
C
SBSY and STS are not sampled during command operations.
A = CBSY setup; half CCLK period.
B = CMD sampled by the print engine.
C = Recovery cycle; half CCLK period.
NOTES:
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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