Piedinature - Pinouts
TI-99/4a Cassette port

9 PIN D-SUB MALE (At the computer)

9 PIN D-SUB FEMALE (At the cassette cable)

Pin	Name	Dir	Comment
1	Cass 1 motor control	OUT	CRU bit 22
2	Dito	OUT	neg
3	Output to tape 2	OUT	CRU bit 25
4	Audio gate	OUT	CRU bit 24
5	Output to tape 2	OUT	neg
6	Cass 2 motor control	OUT	CRU bit 23
7	Dito	OUT	neg
8	Input from tape 1 or 2	IN	CRU bit 27
9	Dito	IN	neg

Note: Direction is Computer relative Cassette.
Cassette 1 can't be written to.

Piedinature - PinoutsTI-99/4a Cassette port