SN76489 / SN94624 (TMS9919) sound generator pinout

DIP-16. Three tone voices and one noise voice, written over an 8-bit data bus.

Three square-wave tone generators, one noise generator, attenuators and an audio summer. TI numbers the data pins MSB first (D0 = MSB on pin 3); boards drawn LSB first call pin 3 D7. Pin 9 is AUDIO IN on the SN94624 (sold as TMS9919) and N.C. on the SN76489AN. The SN94624 is a 500 kHz-clock part; the SN76489AN takes up to 4 MHz. On the TI-99/4A the SN94624 runs from the 447 kHz GROM clock and an SN76489 (some boards) from the 3.58 MHz VDP clock; the sound port is $8400 and pin 9 mixes in cassette and speech audio. No sound: check the clock on pin 14 and +5 V on pin 16 first.

Open the interactive SN76489 pinout

Pins

Pin	Name	Type	Signal
1	D2	data	Data bit 2 in TI numbering (D0 = MSB). In LSB-first numbering this is D5.
2	D1	data	Data bit 1 (TI numbering; D6 LSB-first).
3	D0	data	Data bit 0, the MSB (TI numbering; D7 LSB-first).
4	READY	ctrl	Ready, open collector. Goes low while the chip takes a write (32 clocks on the SN76489AN; the count differs between family members); high = data taken.
5	/WE	ctrl	Write enable. LOW = data on D0-D7 is valid.
6	/CE	ctrl	Chip enable. LOW selects the sound chip.
7	AUDIO OUT	audio	Audio drive output.
8	GND	ground	0 V.
9	AUDIO IN	audio	SN94624 / TMS9919: external audio input, mixed into the output. SN76489AN: N.C., make no connection.
10	D7	data	Data bit 7, the LSB (TI numbering; D0 LSB-first).
11	D6	data	Data bit 6 (TI numbering; D1 LSB-first).
12	D5	data	Data bit 5 (TI numbering; D2 LSB-first).
13	D4	data	Data bit 4 (TI numbering; D3 LSB-first).
14	CLOCK	clock	Clock input. SN76489AN: tone = clock / (32 x N), clock up to 4 MHz. The SN76494 drops the divide-by-8 stage (500 kHz limit, TI data sheet); the SN94624 is taken to match it, but no SN94624 data sheet was checked. UNVERIFIED
15	D3	data	Data bit 3 (TI numbering; D4 LSB-first).
16	Vcc	power	+5 V supply.

SN76489 / SN94624 (TMS9919) sound generator pinout

Pins

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