Print Engine Interface
10-8
MC68322 USER’S MANUAL
MOTOROLA
10.1.5 Printer Communication Interrupt Event Register
The printer communication interrupt event register (PCIER) indicates when a serial
command has been sent or a serial status has been received.
Figure 10-5. Printer Communication Interrupt Event Register
The command sent (CMS) bit indicates that the PCOMR’s printer command field has been
written and that the 8 bits of command data have been sent to the print engine. This interrupt
event bit notifies the core that the command has been sent.
The status receive (STR) bit indicates that a status received interrupt event is active. This
occurs when the interface receives one byte of status data and the SBSY pin is deactivated.
STR is set when the SBSY pin is inactive to prevent a command operation from occurring
before the print engine is ready to receive it.
10.2 PRINTER COMMUNICATION PROTOCOL
The print engine interface uses the CBSY and SBSY pins to indicate the direction of data
transfer and it uses the CCLK pin to pace data transmissions. It does not employ
handshaking, but it asserts the CBSY and SBSY pins before the actual data transmission
so there is sufficient time for the logic to prepare for the subsequent data. CCLK remains
inactive until either the CBSY or SBSY pin is asserted and then goes through eight periods,
one per data bit. During a command transfer to the print engine, the MC68322 shifts a bit on
each CCLK falling edge and expects the print engine to sample the datastream on each
rising edge. Similarly, for a status transfer from the print engine, the MC68322 samples the
datastream on each rising edge and expects the print engine to shift a bit on each falling
edge.
Note: The PCIER is located in the interrupt register portion of the memory map and,
therefore, is not necessarily located contiguously with the other print engine
interface registers.
= RESERVED
15
14
13
12
11
10
9
8
7
65432
1
0
15
14
13
12
11
10
9
8
7
65432
1
0
ENABLE
00FFF720
00FFF722
00FFF724
CMS STR
LEVEL
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
..
.