There is a very distinct family of ECUs found in 88-91ish OBD0 hondas.
The main characteristics of this family:
This architecture was also used by Rover in the UK, and appeared to do so for considerably longer than the 4 years this architecture was used in USDM and JDM cars.
A partial list of OBD0 ECUs:
- PG7 (88-89 Integra D16A1 - note the 86-87 version of this ECU ran the vacuum advance D16A1 motor. Different family)
- PM6 (USDM Civic/CRX Si - D16A6 SOHC)
- PM7 (JDM/EDM Civic/CRX Si - ZC DOHC)
- PM8 (USDM D15B? SOHC HF, EDM D16Z? ZC DOHC)
- PR4 (USDM 90-91 Int
- PR5 (JDM Integra ???)
- PP5 (UKDM Rover Cabio?)
- PS9 (USDM Civic Ex 4dr D16A6 auto???)
- PK2 (JDM Honda Prelude B20A Engine electronic advance)
- PH3 (JDM 86-89 Honda Accord B20A)
Chipping An88-89 ECU is not as easy as the 90-91 computers because only the later computers have replaceable external ROMs.
Understanding OBD0 Inter Chip Communication will be key to figuring out exactly how the ECUs work.
Attached below is an eagle (4.09) library containing the MCU (OKI 8xC154), RAM (M5128), ADC (µPD7004) and engine control counter IC (Oki6260 A) devices for using these components in eagle layout editor.