Panasonic JB-3300 Technical Manual page 217

(c) Speaker interface
The speaker interface circuit amplifies the signal from the 8253 and
outputs it to the speaker. Signal range of 7.4 Hz to 1.19318 MHz is
possible.
8255-5
PBI m™ SPK DATA
PBO mm SPK GATE
So PC5 m SPK FRQ
PC 4 m= SPK OUT +5
_ |
|
S : me
IA 4Y Ww ron.
|
|
+5 |
8253 CLA | |
, |CLA |
75477
OUT 2 -——— I/O Board
|
GATE 2
CPU
Board er
<>] CLK 2s |
Le
1.19318 MHz
Controlled by SPKDATA and SPKGATE output by 8255-5
and by SPKFRO output by 8253. SPKFRO and SPKOUT
are input to 8255-5.
Figure 5-68 Speaker Interface Block Diagram
It - 97