The Apple IIc external disk drive port is a DB-15. The signals available at the port are as follows:
1 - GND
2 - GND
3 - GND
4 - GND
5 - +12V
6 - + 5V
7 - +12V
8 - +12V
9 - /EXTINT
10 - WRPROT
11 - SEEKPH0
12 - SEEKPH1
13 - SEEKPH2
14 - SEEKPH3
15 - /WRREQ
16 - NC
17 - /DR2
18 - RDDATA
19 - WRDATA
CAUTION: Connecting anything other than an Apple Disk IIc to this connector may invaildate your warranty