understanding data semantics and diagram

Question

According to http://www.auto-diagnostics.info/pdf/ford_eectch98.pdf page 10, "The 8361 ROM chip contains 8k bytes of program memory plus 128 bytes of additional RAM."

I found two diagrams under different names "81C61 RAM" and "8763 EPROM". 8763 EPROM 81C61 RAM

It seems to me that the 8763 EPROM has 16K*8 = 128kb of memory while the 81C61 has 8kb of RAM. Are they related to the 8361 chip or are the values just a coincidence? Any suggestions to further explore? (opening the microcontroller etc?)

• user16324: Table 5 "8361" has 8161 in the title so at least the pinout is probably teh same or very closely related. I think the memories have 2x the store you suggest, as the legend is "x16" not x8 (I haven't found how the "Data Out Mux" selects bytes from the 16 bit word, probably from the address LSB.) Intel had a sort of code in those days : 80xx CPU, 81xx ?RAM? 82xx peripheral (e.g. 8251 UART, 8255 GPIO) 83xx ?RAM? 87xx EPROM. Looks like you need to find 40 year old 8096 databooks... One last thought : you might ask on Retrocomputing.
• jsotola: your post is like I found a 1 litre bottle of orange juice and I found a 1 litre bottle of milk. Are these related or are the values just a coincidence?
• user16324: See also embeddedrelated.com/showthread/comp.arch.embedded/62042-1.php and intel.com/Assets/PDF/General/15yrs.pdf. The latter (p.20) suggests the 8361 combines RAM and ROM. (maybe 83xx was mask ROM)
• Jt90: thanks for the reply. will look at the sources later. I thought so too and was checking out some docs specifically on microcontrollers and searching for those that have similar specs to the one i'm investigating. Maybe i've confused microprocessor with microcontroller too, since many instructions and videos online speaks of the microprocessor in general. I found a video and article that speaks of register files as RAM for microcontrollers which was confusing for me

Answer 1

It seems to me that the 8763 EPROM has 16K*8 = 128kb of memory while the 81C61 has 8kb of RAM.

The following are Program Memory Devices:

8361: 8K x 8-bit Masked Read-Only Memory(MROM) with 128x8-bit Static Random Access Memory(SRAM)
8762: 16K x 8-blt U.V. Erasable and Programmable Read-Only Memory(EPROM) with 5-bit read-only port
8763: 32K x 8-bit U.V. Erasable and Programmable Read-Only Memory(EPROM) with 5-bit read-only port

The following are Read/Write Memory Devices:

81C61: (2Kx8-Bit) RAM-I/O and 81C62 (2Kx8-Bit) RAM/CART
81C65: RAM/CART/DUCE and 81C66 RAM/EBC/DUCE
6303: (128x8-Bit) Static RAM

Are they related to the 8361 chip or are the values just a coincidence?

The 8361 device is designed to provide non-volatile memory for program storage as well as additional working memory space for the microprocessor. It is also designed as a multiple applications device where three different 512-byte blocks of data(e.g., calibration look-uptables, constants, etc.)can reside on the device at one time.

The 8763 contain a general purpose memory-mapped 5-bit read-only input port that can be used to extend the input capabilities of a system, or as a coded input for selecting any one of several calibration tables that may be contained with in a device.

The 81C61 is designed to provide additional working memory space for the microprocessors and, in addition to providing serial I/O capabilities to the system via the custom asynchronous receiver/transmitter (CART) which is available on the 81C62 only.

Simplified Block Diagrams: 8361 ROM/RAM Figure D-1 8361 ROM/RAM

8762/8763/87C66/87F66 EEPROM Figure D-2 8762/8763/87C66/87F66 EEPROM

81C61 RAM-I/O and 81C62 RAM/CART Figure D-4 81C61 RAM-I/O and 81C62 RAM/CART

Any suggestions to further explore? (opening the microcontroller etc?)

There are lots of resources if you search 'Tuning EEC-IV' and/or '8061 Disassembly'.

The most active web resource(current as of Jan. 2021) for EEC-IV and EEC-V (8061,8065) CPUs is located at http://efidynotuning.com