Need help with 80C32 MCU info - Page 1
Forum section: electronics / general

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 02:22:17 am
content: Hello!I am working on a project that uses an 80C32 MCU with a 74HC373N and a M27C256 eprom. it's a controller board for a Philips CDPRO2 cd drive unit.I have been doing some google gargling and from what I read...the 80C32 does not have any onboard memory correct? the program should be store entirely on the M27C256 eprom is that correct?The board was a new production board that never worked. or possibly worked then died I am not sure. I am trying to make it work now. I have replaced all the active parts on the board. I looked at the old eprom and compared it to the program in a known good one and it sure looks like the board got zotted and scrambled. So I replaced all the active parts, but, it still is not functioning and I am trying to understand why...SO. that is why I am asking about the 80C32 MCU. without internal memory I am assuming the MCU does not need to be programmed in anyway. that it should be able to be replaced with another one (I have NOS parts) and that the program is in the eprom to make it function.OR...is there some sort of programming stored In the 80C32 even though it does not have internal memory?give me some 101.thanks

author: amyk
author_rank: Super Contributor
timestamp: September 05, 2024, 02:30:11 am
content: Read datasheet and see for yourself:https://www.alldatasheet.com/datasheet-pdf/pdf/224031/INTEL/80C32.html

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 02:48:04 am
content: I have been reading the datasheet but I am not very familiar with Micro controllers so I am not 100% sure what I am looking at? or for! i have no idea.

author: oPossum
author_rank: Super Contributor
timestamp: September 05, 2024, 03:01:03 am
content: https://en.wikipedia.org/wiki/MCS-51#Related_processors

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 03:04:36 am
content: I have read that. I just dont understand it all.i see not much help here. thank you anyway. i will look elsewhere for assistance.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 05, 2024, 07:21:23 am
content: Quote from: Audio101 on September 05, 2024, 02:22:17 am80C52 were ROM parts 80C32 were romless.A simple sanity check is to use a blank EPROM, that is 0xFF, which will just have the PC increment.If there is no other memory space decode, that will wrap and give a binary counter pattern on all address pins.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 05, 2024, 08:42:13 am
content: Yes the 80C32 is ROM less, so the program needs to be in the external EPROM.What might get you better answers as to why it is not working is to post some more information about the board, like schematics if you have them, or pictures of both sides of the board which might allow us to spot a problem on it.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 05, 2024, 08:45:22 am
content: Quote from: PCB.Wiz on September 05, 2024, 07:21:23 amNot inserting an EPROM will do the same if the data bus has pullups.

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 12:52:06 pm
content: AHH thank you! Ok so I am correct about the eprom. THANK YOU for clearing that up. SO replacing the Microcontroller is ok.I will post more info, pictures and schematics.When i first started testing the board. I would notice that the clock would run for 1 second then stop. sometimes 2 seconds. I changed the eprom and now the clock runs continuously but the board is otherwise dead. so I changed all of the parts. and no change. swapped the eprom again with other known good one. and even verified the contents in my eprom programmer. I am beginning to suspect that there is a plated through hole that is not plated all the way through or something that i am not seeing. I have pictures of other production samples of this board, so i am 99% certain that all the parts are correct and facing the right directions etc. I have inspected the board under a bright light looking for shorts or other pcb problems. checked all the resistors. and the only thing i haven't done is ohm out each and every path...which is next.this is the board. as stated earlier, this is a controller board for a CD player. it is based on the Daisy-Laser/Phillips design for the CDPRO2 drive. the schematic is directly from Daisy and is 98% the same as the ARC schematic which is also posted but more confusing to try and sort out. and fyi it can be found on the ARCDB.ws website so I am not posting anything out of line. it is published publicly.I suspect. and it's a total guess is that something is holding the MCU in standby. but I cannot figure out what. there is an IR sensor on another board that sends the MCU commands from the remote control. that SHOULD wake the mcu up and make it function....I don't know enough about micro controllers to know what i am really looking for. googling i read to look at the ALE line to see if the clock is running. and it is. and i confirmed that by scoping the crystal resonator directly which, i was surprised i could actually do that without the scope capacitance massing things up...but i can.I have added sockets to the 3 IC's so make changing them easier. I have an eprom programmer. and i have multiple eproms with various versions of the code both from Daisy and ARC. and I have copied all of them to the computer so i can compare the contents of each eprom for verification etc.the cd drive plugs into this board. I have verified the CD drive works fine. there is also a display board that plugs into this board. I have 4 of those. one of which is brand new. there is a switch board that plugs into the display board. the display board has its own MCU for controlling the VFD display and receives the switch commands and passes them to the controller board...BUT the IR remote control sends data directly to the controller board MCU.I have verified all the power supply voltages are correct. grounds are all there. power is everywhere it should be. all the basic checks.

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 12:52:35 pm
content: Quote from: PCB.Wiz on September 05, 2024, 07:21:23 amthis is very helpful thank you very much!

author: Audio101
author_rank: Contributor
timestamp: September 05, 2024, 12:55:02 pm
content: Quote from: pcprogrammer on September 05, 2024, 08:45:22 amso this is interesting. if i remove the eprom i should see the port pins do a binary pattern? that is an easy test i can try. remove the prom and scope the port pins?

author: Ian.M
author_rank: Super Contributor
timestamp: September 05, 2024, 01:17:04 pm
content: Quote from: pcprogrammer on September 05, 2024, 08:45:22 amSee schematic page 5 (6 in the PDF) - there are no pullups on AD7:0 and as U9 is HC CMOS not bipolar TTL, its inputs wont act as pullups.If you've got a blank EPROM use that to do the test, or if you've socketed U9 and have a 74LS373 handy, swap the HC address latch for a LS TTL one. Adding pullups on a DIL28 header to fit the EEPROM socket probably isn't worth the effort.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 05, 2024, 04:05:11 pm
content: Did you check the PSEN signal in respect to the ALE signal?It might show you why it is not doing what it should do.With a logic analyzer things are even better to check, but you need a lot of inputs to catch all the signals.Edit: The board looks clean and simple enough, and the schematics show the same. You wrote to have replaced the IC's with sockets to make things easier, so these solder joints are all redone. It might indeed be that there is a short somewhere that keeps it from running normally. Check the data and address bus line per line to see if the activity looks normal and the levels are reached.

author: Ian.M
author_rank: Super Contributor
timestamp: September 05, 2024, 04:43:35 pm
content: Other things to check:Level of RESET signal + does it pulse high at powerup (trigger scope in one-shot mode on rising +5V, and monitor RESET with other channel).Substitute a known good 12MHz resonator or crystal.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 05, 2024, 07:53:35 pm
content: Quote from: Audio101 on September 05, 2024, 12:55:02 pmSimply removing the eprom needs strong pullups to be present, which is not common.The BUS outputs address then reads EPROM, so a floating bus cycles through the opcodes, and will do strange things.A blank eprom is simpler.

author: westfw
author_rank: Super Contributor
timestamp: September 05, 2024, 08:09:43 pm
content: You might want to notice that you should be able to drop in an 80c52, 8752 or whatever into the 8032 socket. The schematic says EA/ is grounded, which disables the internal memory (if present), and an 8052 (internal ROM ignored) should behave the same as an 8032 (no internal ROM.)

author: Audio101
author_rank: Contributor
timestamp: September 06, 2024, 03:12:09 am
content: I replaced the crystal resonator tonight. no change. inspected the board again. removed the 2 relays which are not in circuit anyway, but, went through the process of checking them. and I am baffled.I have a Philips/Daisy factory controller on the way from Malaysia. it is supposed to be here next week. same circuit. I can use it to test and compare.

author: Audio101
author_rank: Contributor
timestamp: September 06, 2024, 03:13:24 am
content: Quote from: westfw on September 05, 2024, 08:09:43 pmInteresting. Ok. I may order some additional controllers.