Help, how can I connect after replacing the RAM chip - Page 1
Forum section: electronics / projects

author: daisizhou
author_rank: Super Contributor
timestamp: August 31, 2023, 09:30:39 pm
content: Hello everyone, thank you for watching.In my spare time, I am rebuilding a PCB project，I cannot obtain the real PCB motherboard and measure it because it is in another city far away from me,At present, I only have physical photos and firmware of this PCB motherboard, as well as the circuit schematic of the old versionThe main MCU and PLD chips have always been MC68HC11G5FN and 22V10Z,The new version has replaced RAM and ROM chips,Replace the ROM chip from 27C010 to 27C1001, and the RAM chip from LH5160 to LH5164A.LH5160 address input from A0-A14, a total of 15 channels,And connect bus uPA0-uPA14, a total of 15 channels.Lh5164 address input from A0-A12, a total of 13 channels.If LH5164A is used to replace LH5160，So how should uPA13 and uPA14 be connected?The 30th pin of 27C010 is A17, while the 30th pin of 27C1001 is NA，How should I connect them?How can I connect all the pins on the PLD 22V10Z chip?If you know, please let me know. Thank you

author: wasedadoc
author_rank: Super Contributor
timestamp: August 31, 2023, 10:45:37 pm
content: Why do you think the LH5160 has A0 to A14? The datasheet says A0 to A12 which is consistent with it also saying it is an 8k by 8 chip. Which the LH5164 is too.

author: daisizhou
author_rank: Super Contributor
timestamp: August 31, 2023, 11:50:04 pm
content: Because I checked the schematic diagram and found that the IC16 model is LH5160D，I understand that LH5160 only has 28 pins and the address input is A0-A12It seems that the schematic diagram is incorrect, which is what confuses me

author: daisizhou
author_rank: Super Contributor
timestamp: September 01, 2023, 04:03:11 am
content: I have redrawn the schematic, but I don't know how to connect the RAM chips LH5164 "CE1", "CE2", "WE", "OE"

author: srb1954
author_rank: Super Contributor
timestamp: September 01, 2023, 08:04:02 am
content: Quote from: daisizhou on August 31, 2023, 11:50:04 pmIt looks like the schematic provides for an upgrade to larger RAM and EPROM chips than what is installed in the PCB. The extra address lines allow for an 32kx8 RAM and a 256kx8 EPROM.

author: srb1954
author_rank: Super Contributor
timestamp: September 01, 2023, 08:08:01 am
content: Quote from: daisizhou on September 01, 2023, 04:03:11 amThe pins correspond as follows:W = WEG = OEE = CE1CE2 is unused should be connected to +5V.Do you have the programming information for the 22V10 PLA chip? Without the appropriate programming information this chip won't work and none of the rest of the circuitry will function.

author: daisizhou
author_rank: Super Contributor
timestamp: September 01, 2023, 08:41:46 am
content: I read the 22V10 firmware, but I don't understand how 22v10 worksAlso, please note that,I read the 22V10 hardware version of the firmware, and the corresponding RAM chip is LH5164AD, which is the DIP28 version，address input from A0-A12I found a 256MB RAM chip, which is HM62256A，It's a DIP28 package,address input from A0-A14.Can I use HM62256A to load the circuit (using the 22V10 firmware corresponding to LH5164)?Because of the address bits, CSRAM, RWRAM, OE, these signals look the same as the schematic

author: srb1954
author_rank: Super Contributor
timestamp: September 01, 2023, 11:17:55 am
content: Quote from: daisizhou on September 01, 2023, 08:41:46 amSince the 22V10 handles the address decoding and memory bank switching for this system you need to decode the 22V10 configuration and fully understand how it works.Most likely there was different versions of the 22V10 depending on which size or RAM and EPROM was fitted to this PCB.

author: daisizhou
author_rank: Super Contributor
timestamp: September 01, 2023, 12:41:55 pm
content: A friend of mine helped me analyze the internal logic of 22V10. Here is a picture of it.I am a beginner and not good at analyzing logical components.If you know, please let me know. Thank you

author: daisizhou
author_rank: Super Contributor
timestamp: September 02, 2023, 03:54:34 am
content: Can anyone know what this logic diagram means?

author: srb1954
author_rank: Super Contributor
timestamp: September 02, 2023, 04:12:36 am
content: Quote from: daisizhou on September 02, 2023, 03:54:34 amYou need to do some reading on PAL logic chips. A good place to start would be the Wikipedia article, which lists the manufacturers of PAL devices. Most manufacturers of these devices had extensive literature or application notes describing how a PAL chip works and how to use it.As these devices are mostly obsolete you might have to search through the internet archives for such information as practically all of the original manufacturers of these devices have dropped this product line or the companies have been swallowed up into larger companies or have just disappeared.