Sh docs

Renesas (previously Hitachi) makes the SuperH microcontrollers used in Nissan ECUs:
 * SH7055 (older version, mfg by Hitachi)
 * SH7055s
 * HD64F7058 - older version, mfg by Hitachi
 * SH7058 - Renesas
 * SH7058S
 * SH72531 ?

You need BOTH these documents:
 * 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.

7055 / 7058 "versions"
These 705x ICs were manufactured initially by Hitachi up until ~2002-2003 ? Then by Renesas for the following years. For 7055 (HD64F7055 / SH7055), at some point the silicon process size also changed from 0.35um to 0.18um. The impact of this is MAJOR when it comes to reflashing. The ROM/FLASH registers are totally different; they require vastly different code to reflash them.

As for the old vs new 7058 ICs, there appears to be no such change, i.e. the same registers are used and the reflash process is the same, hence the same code can be used.

How to tell between 7055 versions

 * Package markings :
 * 7055 : 0.35um :"64F7055F40", 0.18um "64F705548" According to Shuher@RR, the last digit seems to indicate process size.
 * 7058 : both "64F7058F80"
 * The model name may be different (not sure how to determine this, however)
 * 7055 : old = HD64F7055R, new = HD64F7055S
 * 7058 : possible typo in the old datasheet; old=HD64F7055S, new = HD64F7058BF80(L/K)
 * "Supported Device Inquiry" command in SHBootmode, unfortunately the DS isn't overly clear about the expected response.
 * FID IC string in the ROM ? This is unverified, but maybe "705507" is 0.35um, and "705513" and onwards is 0.18um ?
 * It should be possible to read/write certain FLASH registers and observe behavior. For instance, FKEY is only implemented on 0.18um devices, etc.