Other Circuits; Speaker Circuit - IBM XT 5160 Technical Reference

Other Circuits
Speaker Circuit
The system unit has a 57.15 mm (2-1/4 in.) audio speaker. The
speaker's control circuits and driver are on the system board. The
speaker connects through a 2-wire interface that attaches to a
3-pin connector on the system board.
The speaker drive circuit is capable of approximately 1/2 watt of
power. The control circuits allow the speaker to be driven three
different ways: 1.) a direct program control register bit may be
toggled to generate a pulse train; 2.) the output from Channel 2
of the timer/counter may be programmed to generate a waveform
to the speaker; 3.) the clock input to the timer/counter can be
modulated with a program-controlled I/O register bit. All three
methods may be performed simultaneously.
PPI Bit 1, I/O Address Hex 0061-+ ~
1.19 MHz
NAND
Clock
-+
In 2
Low
Timer Clock Out 2 -+
~
Driver
~
Pass ......To
-+
Gate 2
Fi 1ter Speaker
-
PPI Bit 0, I/O Address Hex 0061
Speaker Drive System Block Diagram
Channel 2 (Tone generation for speaker)
Gate 2 -- Controlled
by
8255A-5 PPI Bit (See 8255 Map)
Clock In 2 -- 1.19318 MHz OSC
Clock Out 2 -- Used to drive speaker
Speaker Tone Generation
1-26 System Board