REV.-A
2.3.3 Main
IC
Functions
This section describes the functions of the main ICS in the PEGX board control circuit.
2.3.3.1 CPU Functions
The printer employs the
pPD78 10HG CPU. The CPU processes data using a 3.685 MHz clock which
is 1/4 of the external clock (14.74 MHz.)
The CPU is reset when the reset signal (pin 28: LOW) is input, and executes the external program (4A,
PROM) from address O.
The CPU controls all of the printer operations either directly or indirectly. The external memory area
is expanded to 64K bytes so that the CPU can control the internal RAM, external ROM (4A: program
and character generator), external SRAMS (5A and 6A), and the E05A16G and E05A15A gate arrays
(7A and 3A).
NOTE: Refer to Section 2.3.1.3 for memory mapping.
This CPU includes an 8-bit analog-to-digital converter, timer-event counter, and serial interface. These
functions can be set in units of bits using the mode register for each port, and are used with general
1/0 ports (excluding the analog-to-digital converter.)
Table 2-3 shows the port assignments. (Refer to the Appendix for details on the CPU.)
Table 2-3. Pin Function
of
CPU
Pin No. Signal Name
Direction
Function
1
PAO
—
Not used.
I
I
6
PA5
7
PA6
IN
AUTO FEED XT signal/DIP switch 2-4
8 PA7
IN
SLCT IN signal/Jumper J 1
9
PBO
IN
DIP switch 1-1 to 1-8
I
I
16
PB7
17
Pco
OUT
TXD data output
18
Pcl
IN
RXD data input
19
PC2
—
Not used
20
PC3
IN
ON-LINE switch interrupt input
21 PC4
—
Not used
22
PC5
IN
P/S (Parallel/Serial) data transfer selection signal
input
23
PC6
OUT
PWD signal output
24
PC7
OUT
Paper feed motor driving control output
25
NM 1
—
Not used
2-27
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