8253 Programmable Interval Timer; Printer Interface - Sharp mz-800 Technical Reference And User's Manual

6 8253 Programmable Interval Timer
The 8253 makes sound generated with the counter #0
and internal timer is operated with the counters #1 and
#2.
• Counter mode
#0 ..... Square waveform generator MODE3
#1 ..... Rate generator MODE2
#2 ..... Interrupt on terminal counter
8253
(8255) PC2
on
INT
I
DTO
CLK 2
A01
ADO
HSYN
(PlO) PA4
RO
(PSG) Audio · in
(8255) PCO
WR
CKMS (1.10 MHz)
C53
SJG
• The counter #0 counts input pulse of 1.1 MHz,
divided by the predetermined rate (musical score
data) to generate sound. lt is connected with the
mixing audio amplifier through AUDIO-IN of the
sound IC (76489AN).
This counter output is gated by PC of the 8255 port
C,
and the counter gate is controlled by 001 of $E008.
The counter #0 output is also used for interrupt
control INTO and connected to A4 of the Z-80A PlO
port A.
• The counter #1 counts pulse of 15.6 kHz and gener-
ated a pulse on OUT1 at every second. The counter
#2 counts pulses and makes OUT2 turned high.
OUT2 outputs becomes
TNT
via the gate and is
connected to INT of the CPU.
7 Printer interface
The Z-80A PlO is used for the printer interface. lt has a
pair of 8-bit 1/0 ports.
28
!
Do
o,
02
Data bus
8!
Os
o.
07
{
BI"A
CID
PlO _
control
C£.
M1
IORQ
Ri5
+5V
GNO
Interrupt IEI
{
INT
control lEO
Z.3C:-P ·-::,
Z8C:A-P ::;
Pin configuration
Ao
A,
A2
A,
A.
As
Port A
As
A1
AROY
ASTB
13')
l
a,
B2
a,
B,
Bs Port B
a.
I
B1 1
BRDYJ
BSTB