8253 Programmable Interval Timer; Printer Interface - Sharp MZ-800 Service Manual

MZ-800
4-4. 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
DD
D7 OUT 2
INT
I
I
DTO
DO ClK 2
AD1
A1 OUT1
ADO
AO
ClK 1 HSYN
(PlO) PA4
RD
OUTO
(PSG) Audio· in
RD
(8255) PCO
WR
WR ClK 0
CKMS (1.10 MHz)
C53
CE GATE 0 53G
• The counter #0 counts input pulse of 1.1 MHz,
divided by the predetermined rate (musical score
data) to generate sound. It 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 INT via the gate and is
connected to INT of the CPU.
4-5. Printer interface
The Z-80A PlO is used for the printer interface. It has a
pair of 8-bit 1/0 ports.
31
r
Do
D,
D,
Data bus
1
8!
Ds
Ds
D7
{
BlA
CID
PlO
control
GE.
M1
10Ra
fill
+5V
GND
Interrupt IEI
{
INT
control IEO
78/'- p
,''0
A - c'
Pin configuration
Ao
A,
A,
Aa
A.
As
pon A
7
~
ARDY
ASTB
Ba
f
B,
B,
B3
B.
B s Pon B
Bs
B7
E!HDYJ
BSTB