Sh docs

Renesas (previously Hitachi) makes the SuperH microcontrollers used in Nissan ECUs:
 * SH7055
 * SH7055s
 * SH7058
 * SH7058S
 * SH72531 ?

You need:
 * 1) the datasheet for your particular ECU, such as "REJ09B0046" for sh7058.
 * 2) the appropriate "software manual" for the ECU family, like REJ09B0316 - SH-2E Software manual . This describes the architecture and instruction set.