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The 82C55 is an IO controller chip used in many OBD1 ECUs.

Fortunately, almost all OBD1 Civic Integra ECUs share a common pattern for what is controlled by the 82C55 chip. Vernon (Deluded) took the time to electrically map what is connected to the 82C55 on these ECUs.

A datasheet is available here, except the 82C55 used in Honda ECUs mysteriously has two extra pins -- my guess is they're 17 and 37, both unused. The code sets the control register to 0x90, which means it uses so-called Mode 0, port A is an input, and ports B and C are outputs.

I/O 82C55 pin element element pin function
I 1 A/D board   PA3 <- tps/vss diagnostic?
I 2 R114   PA2 <- (paired with R109?)
I 3 R113   PA1 <- (paired with R110?)
I 4 R112   PA0 <- (paired with R111?)
  5 66207 24 /RD signal, both 82C55 and 66207
  6 66207 15 82C55 /CS <- 66207 A14
  7 gnd   Vss
  8 66207 14 82C55 A1 <- 66207 A13
  9 66207 12 82C55 A0 <- 66207 A12 ''(shouldn't that be pin 13?)''
O 10 knock resistors   PC7 -> knock diagnostic?
O 11 Q16 1=control PC6 -> ultimately controls EGR sol
O 12 R134   PC5 -> 10Kohm pull-up resistor
O 13 Q46 1=control PC4 -> ultimately controls MIL
O 14 IC14 2=control PC0 -> VTEC sol control
O 15 IC13 2=control PC1 -> IC13 / pre-vtec control
O 16 Q12 1=control PC2 -> ultimately controls O2 Heater
  17 unused    
O 18 knock resistors   PC3 -> knock diagnostic?
O 19 7U016 3 PB0 -> 7U016
O 20 Q14 1=control PB1 -> ultimately controls purge sol
O 21 Q37 1=control PB2 -> ultimately controls alternator
O 22 Q13 1=control PB3 -> ultimately controls rad fan
O 23 IC15 2=control PB4 -> IC15 / Auto trans lockup solenoid A
O 24 Q17 1=control PB5 -> aib/shift light control/q34 auto lockup
O 25 RM13 8 PB6 -> 10kohm resistor: pull up
O 26 7U016 10 PB7 -> 7U016
  27 5V   Vcc
  28 66207 8 D7
  29 66207 7 D6
  30 66207 6 D5
  31 66207 5 D4
  32 66207 4 D3
  33 66207 3 D2
  34 66207 2 D1
  35 66207 1 D0
  36 7U016 39 RESET?
  37 unused    
  38 RM13 9 10kohm resistor: pull up - WR also?
I 39 A/D board   PA7 <- tps/vss diagnostic?
I 40 Q30 2=o/p PA6 <- diag for O2 heater
I 41 Q26/101 2=o/p PA5 <- diag for IC14=Vtec sol 1720,1980/11F0
I 42 Q28 2=o/p PA4 <- diag for IC15

Notes: intake resonator control doubles up: IC16(3) to Q27(2) to IC9(6)

Attachment?: Modify: Size: Date: Who: Comment:
MSM82C55A-2RS-GS-VJS.pdf mod 193605 16 Mar 2004 - 20:49 blundar Datasheet for the Oki 82C55 as used in ECU.

Revision: r1.3 - 01 Aug 2005 - 14:37 GMT - blundar { Edit | Attach | History | More }
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