Computer buses and slots connectors pinouts  > Apple pinouts
Expansion Slot Connector for the Apple II Series Interface/Add On Cards

Connector is 50 Pin Female Edge. The Bus got modified over the various versions of Apple IIs (Pin 19,35,39)

Motherboard
Pin
Name Direction Description
1 /IOSEL I/O Select. Active when page $Cn gets accessed. N.C. on slot 0
2 A0 Buffered address bus
3 A1 Buffered address bus
4 A2 Buffered address bus
5 A3 Buffered address bus
6 A4 Buffered address bus
7 A5 Buffered address bus
8 A6 Buffered address bus
9 A7 Buffered address bus
10 A8 Buffered address bus
11 A9 Buffered address bus
12 A10 Buffered address bus
13 A11 Buffered address bus
14 A12 Buffered address bus
15 A13 Buffered address bus
16 A14 Buffered address bus
17 A15 Buffered address bus
18 R/W Buffered Read/Write signal.
19 SYNC Only Slot 7. SYNC from Video Generator. Not on Rev 0 Boards. Testpin on Slot 1 for //e
20 /IOSTRB I/O Strobe. Active when $C800 and $CFFF gets accessed
21 /RDY Activation during Phi1 will halt the CPU, with the address bus holding the last address
22 /DMA Activation disables the 6502s address bus and halts the CPU
23 /INTOUT Daisy-chained interrupt output to lower priority devices
24 /DMAOUT Daisy-chained DMA output to lower priority devices
25 +5V +5 Volt power supply. Max. 500mA for ALL peripheral boards
26 GND System electrical ground
27 /DMAIN Daisy-chained DMA input from higher priority devices
28 /INTIN Daisy-chained interrupt input from higher priority devices
29 /NMI Non-Maskable Interrupt. Monitor ROM starts interrupt handling routine at location $3FB
30 /IRQ Interrupt ReQuest. Monitor starts the routine pointed to by $3FE/F
31 /RES RESet
32 /INH INHibits the on board ROMs ($D000-$FFFF)
33 -12V -12 Volt power supply. Max. 200mA for ALL peripheral boards
34 -5V -5 Volt power supply. Max. 200mA for ALL peripheral boards
35 COLORREF Only Slot 7. 3.5 MHz Video COLOR REF. Not on Rev 0 Boards. Testpin on Slot 1 for //e. M2B0 on A2gs
36 7M 7Mhz clock
37 Q3 2Mhz asymetrical clock
38 PHI1 1 MHz phase 1 clock
39 Various USER1 on A2: Disable adressdecode. 65C02 SYNC on A2e. M2SEL on A2gs
40 PHI0 1 MHz phase 0 clock (Inverted PHI1)
41 /DEVSEL DEVice SELect. Active when $C0nX gets accessed; n - Slot#+8
42 D7 Buffered bi-directional data bus
43 D6 Buffered bi-directional data bus
44 D5 Buffered bi-directional data bus
45 D4 Buffered bi-directional data bus
46 D3 Buffered bi-directional data bus
47 D2 Buffered bi-directional data bus
48 D1 Buffered bi-directional data bus
49 D0 Buffered bi-directional data bus
50 +12V -?- +12 Volt power supply. Max. 250mA for ALL peripheral boards

unknown connector
According to 3 reports in our database (0 positive and 1 negative) this pinout may be incorrect.

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