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Non-ugly version of diagrams will be available as soon as I magically acquire talent.


Apple// Internal Slot
(Hereafter referred to as the 'Apple Bus')

__
Figure 1.0 Apple Bus

Figure 1.1 Card Edge Dimensions

Figure 1.1 Card Edge Dimensions
__A. 7.62 mm Card edge depth
__B. 1.778 mm Finger width
__C. 2.54 mm Finger spacing

Table 1.0 Apple Bus Pinout Description

Pin
Name
______Description
1
I/O SEL
Normally high; goes low during phase 0 when the 6502 addresses location $CnXX, where n is the connector number. This line can drive 10 LS TTL loads.
2
A0
Three-state address bus. The address becomes valid during phase 1 and remains valid during phase 0. Each address line can drive 5 LS TTL loads.
3
A1
4
A2
5
A3
6
A4
7
A5
8
A6
9
A7
10
A8
11
A9
12
A10
13
A11
14
A12
15
A13
16
A14
17
A15
18
R/W
Buffered read/write line. Valid at the same time as the address bus; high during a read cycle, low during a write cycle. It can drive 2 LS TTL loads.
19
SYNC
Composite horizontal and vertical sync, on expansion slot 7 ONLY. This line can drive 2 LS TTL loads.
20
I/O STR
Normally high; goes low during phase 0 when the 6502 addresses a location between $C800 and $CFFF. This line can drive 4 LS TTL loads.
21
RDY
Input to the 6502. Pulling this line low during phase 1 halts the 6502 with the address bus holding the address of the location currently being fetched. This line has a 3300 ohm pullup resistor to +5V.
22
DMA
Input to the address bus buffers. Pulling this line low during phase 1 disconnects the 6502 from the address bus. This line has a 3300 ohm pullup resistor to +5V.
23
INT OUT
Interrupt priority daisy-chain output. Usually connected to pin 28.
24
DMA OUT
DMA priority daisy-chain output. Usually connected to pin 22.
25
+5V
+5V power supply. A total of 500mA is available for all accessory cards.
26
GND
System common ground.
27
DMA IN
DMA priority daisy-chain input. Usually connected to pin 24.
28
INT IN
Interrupt priority daisy-chain input. Usually connected to pin 23.
29
NMI
Non-maskable interrupt to 6502. Pulling this line low starts an interrupt cycle with the interrupt-handling routine at location $03FB. This line has a 3300 ohm pullupresistor to +5V.
30
IRQ
Interrupt request to 6502. Pulling this line low starts an interrupt cycle only if the interrupt-disable (I) flag in the 6502 is not set. Uses the interrupt-handling routine at location $03FE. This line has a 3300 ohm pullup resistor to +5V.
31
RES
Pulling this line low initiates a reset routine.
32
INH
Pulling this line low during phase 1 inhibits (disables) the memory on the main circuit board. This line has a 3300 ohm pullup resistor to +5V.
33
-12V
-12V power supply. A total of 200mA is available for all accessory cards.
34
-5V
-5V power supply. A total of 200mA is available for all accessory cards.
35
3.58Mhz
3.58MHz color reference signal, on slot 7 ONLY. This line can drive 2 LS TTL loads.
36
7Mhz
System 7MHz clock. This line can drive2 LS TTL loads.
37
Q3
System 2MHz asymmetrical clock. This line can drive 2 LS TTL loads.
38
PHASE 1
6502 phase 1 clock. This line can drive 2 LS TTL loads.
39
uPSYNC
The 6502 signals an operand fetch by driving this line high during the first read cycle of each instruction.
40
PHASE 0
6502 phase 0 clock. This line can drive2 LS TTL loads.
41
DEV SEL
Normally high; goes low during phase 0 then the 6502 addresses location $C0nX, where n is the connector number plus 8. This line can drive 10 LS TTL loads.
42
D0
Three-state buffered bi-directional data bus. Data becomes valid during phase 0 high and remains valid until phase 0 goes low. Each data line can drive one LS TTL load.
43
D1
44
D2
45
D3
46
D4
47
D5
48
D6
49
D7
50
+12V
+12V power supply. A total of 250mA is available for all accessory cards.


___The Apple bus is a standardized¹ interface for peripheal expansion of the Apple 2 family of personal computers.² It consists of a fifty pin card edge connector for peripheal cards, and the associated slot on the Apple 2 mainboard. Minor differences exist between the computers within this family, and also between the slots on a single mainboard, depending on position. Typical peripheal cards do not directly fit into the backplate of the computer, as do more popular bus architectures. Connectors generally connect to a card via a ribbon cable, and are attached to the back plate with screws.

1. As standardized as any other expansion slot.
2. The Apple//c computer has no internal expansion slots.


Apple// Expansion Card
Max Dimensions


Figure 1.2 Apple// Card Max. Dimensions

Figure 1.2 Apple// Card Max. Dimensions
__A. 10.75" Total Length
__B. 0 Height
__C. 7.75" Top Length
__D. 15° Slope Angle
__E. 2" Frontal Height
__F. 0 Frontal Length

___The Apple// series of computers

Special thanks to Wayne S., Brian V., and Aaron P. of comp.sys.apple2 !