Tandy PC-6 User Manual

Buzzer Control Circuit
There
are 3 ways to operate the buzzer:
Key
input, BEEP 0, and BEEP 1
8
Mode
Frequency
Time
BEEPO
0.9 kHz
110
msec.
BEEP 1
4.55 kHz
110
msec.
Key Input
4.55 kHz
11 msec.
A
82 t----=1..-
..,.,....,
81 ----
M864H193
A ---.fLJLJL
8LSlSlJ
Interrupt Circuit
• Interrupt circuit for the clock pulse when VDD2 drops.
1. When the power is on, VDD2 is "L" level.
2.
PG2 through the IC and 26th pin of the CPU receive PG2.
3. When VDD2 drops, the output of the IC becomes "GND" level and the CPU does not receive
PG2.
PG1
HD61747825
f--- PG2
VDD2
• Interrupt circuit for the voltage of the Gate Array and options when VDD2 and SW drop.
1. When the power is on, VDD2 and SW is "L" level.
2.
VDD2 for Gate Array and VDD4 is also "L" level.
3.
When VDD2 drops, VDD2 for Gate Array and VDD4 becomes "GND" level and stops the op-
ration of the RAM and options.
sw~
VDD2(from IC 4) VDD4
VDD2(from IC 2)
Keyboard
HD61747B25 controls the upper keyboard.
Ks2
Ks3'VKs8
Upper
HD6174782
Ks9, Ks10
~
KeYboard
HD61747B20 controls the lower keyboard.
Km1'VKm4
Km5'VKm10
Lower
HD6174782
Keyboard
Km11, Km12
-6-

Tandy PC-6 Specifications

General

Brand	Tandy
Model	PC-6
Category	Calculator
Language	English