Okay, so I did some more tinkering today with my MEP-805b generators, and I have discovered some more information that might be useful to others:
So far, I have determined that there are at least 3 different designs of CIMs. Each design has unique hardware and software. There are likely more than 3 designs, but the following is what I have encountered so far:
CIM differences
Type 1: Monochrome display, software version 1.1. I have not investigated this hardware or software much. Two RS232 DB9 serial ports (P20 and J26), one DB25 parallel port (J29), all via external ribbon cable (P27 connector).
Type 2: Color display, software version 4.1.1a, uses a Winsystems SAT-520PLUS motherboard, 64 megabyte stick of ram, a 32 megabyte MD2202-D32-X M-systems DiskOnChip (removable). Same I/O connections as Type 1 above.
Type 3: Color display, software version 4.2, uses a Winsystems PPM-GX500 motherboard, 128 megabyte stick of ram, a 128 megabyte CompactFlash card. Two RS232 DB9 serial ports (P20 and J26) via external ribbon cable, one USB located on the side of the CIM, J29 parallel port is not physically connected inside CIM even though it may be present on the generator itself.
I've also seen videos on YouTube of generators running software version 4.1.2. I'm not sure if it runs on Type 2, Type 3, or another unique CIM (hardware wise).
Reloading software:
The only software I have access to is for Type 2 above. To load the software onto a type 1 or type 2 CIM, a male to male parallel Laplink (null modem) cable is needed, and a PC with a parallel port. I'm assuming Type 3 requires a USB flash drive or something similar to reload the software. The J29 parallel port for type 1 and type 2 CIMs appears to have no function other than software installation.
Serial Ports:
The two serial ports (P20 and J26) are for communication between the I/O Module and CIM (P20), and for the keypad (J26). The keypad is simply a serial mouse, and a serial mouse can be used instead. The other serial port communicates at 57,600 baud with the I/O module. P20 can be disconnected from the I/O module and can be connected to a PC with a null modem cable, and the CIM can be controlled using the test/simulation programs on the software CD that came with the generator. This is a useful diagnostic tool.
Communication Receptacle and remote display software:
The communication receptacle (J3) on the front panel of the generator is not connected to the CIM, but rather to J21 at the I/O module. It is not RS232 serial data like the CIM's serial ports, but rather RS485/RS422. To use the remote display software that came with the generator (again, I've only tried this with software version 4.1.1a), you'll need a USB to RS485/422 adapter. I have this one:
https://www.amazon.com/GearMo-Conve...?ie=UTF8&qid=1483835901&sr=8-7&keywords=rs485
To get this to work, you'll need to do the following: Install the driver for the USB to RS485/422 device, navigate to the device settings in Device Manager and change the device to com4, baud rate to 57,600. You'll need to build a cable from the USB device to the Communication Receptacle using an Amphenol 22-20P connector (male pins) with the following pinout:
USB adapter pin ----> Communication Receptacle
Pin 1 Send (A+) ----> Pin H
Pin 2 Send (B-) ----> Pin B
Pin 3 Receive (A+) ----> Pin D
Pin 4 Receive (B-) ----> Pin F
Hopefully this is helpful information. As I tinker and reverse-engineer more, I'll provide updates. Also, please keep in mind that while I've tried to ensure the information above is correct, it has all been obtained by my own personal observations, measurements, etc. Please use your best judgement when tinkering with your own generator in case I've made a mistake with something.