Pin Out Information

The pins out as follows, looking into the edge­connectors on the back­side:

• Pin A1 is at the bottom left.
• Pin B1 is at the top left.

The edge fingers are on a 2.54mm pitch, some positions are not used but still counted.

Expansion Bus

• 33 pins wide, 63 out of 66 pins used:

      A1  : Right Audio In     B1  : Left Audio In
      A2  : ¬RFSH              B2  : ¬WR
      A3  : ¬RD                B3  : ¬IORQ
      A4  : nc                 B4  : nc
      A5  : ¬MREQ              B5  : ¬NMI
      A6  : A8                 B6  : A9
      A7  : A10                B7  : A11
      A8  : A12                B8  : A13
      A9  : A14                B9  : A15
      A10 : A0                 B10 : A1
      A11 : A2                 B11 : A3
      A12 : A4                 B12 : A5
      A13 : A6                 B13 : A7
      A14 : D0                 B14 : D1
      A15 : D2                 B15 : D3
      A16 : D4                 B16 : D5
      A17 : D6                 B17 : D7
      A18 : ¬RESET             B18 : ¬INT
      A19 : ¬WAIT              B19 : 0V
      A20 : ¬MI                B20 : 0V
      A21 : 1 MHz Clock        B21 : 0V
      A22 : ¬EXP               B22 : 0V
      A23 : 8 MHz Clock        B23 : 0V
      A24 : EC0                B24 : EC1
      A25 : EC2                B25 : EC3
      A26 : ¬EXTC              B26 : A16
      A27 : A17                B27 : A18
      A28 : A19                B28 : A20
      A29 : A21                B29 : A22
      A30 : 0V                 B30 : VSYNC
      A31 : 0V                 B31 : nc
      A32 : HSYNC              B32 : 0V
      A33 : +9V                B33 : +9V     

Note: What I don't understand here is the presence of what appears to be a 23rd address line (A22). Only 22 are required to accomodate a 4­MByte address space. Please tell me if you know what's wrong

Control 1 / Control 2

• 6 pins wide, 9 out of 12 pins used:

       A1 : Keyboard J (Common) B1 : OV
       A2 : Keyboard L          B2 : nc
       A3 : nc                  B3 : nc
       A4 : KB4/9 (Right)       B4 : +5V
       A5 : KB2/7 (Down)        B5 : KB3/8 (Left)
       A6 : KB0/5 (Fire)        B6 : KB1/6 (Up)            

  The numbers appearing after the slashes apply to control 2.
  
  
• All signals are at TTL levels.
• Read as part of the keyboard matrix.
• Use multi­core screened cable.

Printer

• 7 pins wide, 12 out of 14 pins used:

       A1 : 0V                  B1 : 0V
       A2 : ¬STROBE             B2 : ¬READY
       A3 : DATA 3              B3 : DATA 4
       A4 : nc                  B4 : nc
       A5 : DATA 2              B5 : DATA 5
       A6 : DATA 1              B6 : DATA 6
       A7 : DATA 0              B7 : DATA 7                

• All signals are at TTL levels.
• Use 12­way flexible ribbon cable.

Serial / Network

• 4 pins wide, 6 out of 8 pins used:

       A1 : Reference           B1 : 0V
       A2 : nc                  B2 : nc
       A3 : RTS                 B3 : Data Out
       A4 : CTS                 B4 : Data In               

• Signal levels relative to 0V line:
  
  

  0 = 0V

  1 = +12V
  
  

• Signal levels relative to reference line:
  
  

  0 = -5V

  1 = +7V
  
  

• Reference is an offset 'ground', this may not be possible with certain equipment configurations.
• For networking connect RTS to CTS to form the control bus, and connect 'data in' to 'data out' to form the data bus.
• Use 6­core screened cable.

Monitor / Audio

• 7 pins wide, 12 out of 14 pins used:

       A1 : Green signal        B1 : nc
       A2 : 0V                  B2 : 0V
       A3 : Composite Video     B3 : Blue signal
            (Monochrome)
       A4 : ¬HSYNC              B4 : Red signal
       A5 : ¬VSYNC              B5 : ¬CSYNC
       A6 : nc                  B6 : Mode Switch (Peritel)
       A7 : Left Audio          B7 : Right Audio           

• All syncs are at TTL levels.
• Red, Green and Blue signals are 0 to 4 volts linear.
• Use multi­core screened cable.