Via VT82C41N DIP-24 Keyboard Controller (KBC) - help completing pinout \ VOGONS

Via VT82C41N DIP-24 Keyboard Controller (KBC) - help completing pinout

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First post, by maxtherabbit

Posted on 2021-02-04, 00:54

maxtherabbit Offline

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I have a Lucky Star LS-486E board, which I know is a pretty popular board on this forum. My particular revision of the board has this VT82C41N KBC and does NOT have a footprint for a standard DIP-40 KBC. I have been buzzing out the pins on this unusual DIP-24 keyboard controller because it is totally undocumented, as far as I can tell. Here's what I have so far:

1-???
2-???
3-SYSCLK (connected to the southbridge on my mobo, equivalent to B20-CLOCK on ISA)
4-RESET#
5-KBROMCS#
6-IOR#
7-XA2
8-IOW#
9-XD3
10-XD4
11-XD5
12-XD6
13-XD7
14-Vss
15-XD2
16-XD1
17-XD0
18-???
19-KBDINH# (keylock)
20-IRQ1
21-KBDI (connected to keyboard data pin on the DIN)
22-KBCI (connected to keyboard clock pin on the DIN)
23-???
24-Vcc

As you can see I have mapped all of them except pins 1, 2, 18 and 23.

It has come to my attention that there is another revision of this board which contains nested footprints for this mini-KBC as well as a full size DIP-40 footprint.

If anyone has one of these, could you please check for me which, if any, pins on the DIP-40 footprint correspond to pins 1, 2, 18 and 23 on the DIP-24 footprint?

Reply 1 of 3, by Tiido

Posted on 2021-02-04, 07:52

Tiido Offline

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I have a board with a small keyboard controller, I went to find it and it was even smaller one in just DIP20 package by Lance Corp...
It is possible that these 4 pins are not connected internally. You can actually test for it with a diode test, see if these pins give a reading when you test against GND and VCC, connected pins usually always have ESD protection diodes attached and the test will show them.

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Reply 2 of 3, by maxtherabbit

Posted on 2021-02-04, 15:09

maxtherabbit Offline

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Tiido wrote on 2021-02-04, 07:52:

I have a board with a small keyboard controller, I went to find it and it was even smaller one in just DIP20 package by Lance Corp...
It is possible that these 4 pins are not connected internally. You can actually test for it with a diode test, see if these pins give a reading when you test against GND and VCC, connected pins usually always have ESD protection diodes attached and the test will show them.

good idea!

Reply 3 of 3, by maxtherabbit

Posted on 2021-02-04, 21:12

maxtherabbit Offline

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Location: Richmond, VA

Ok by using the diode test I have confirmed that those pins ARE connected to something. Also I have determined that there is no separate TTL logic on the board to handle inverting the KBC clock/data output like there would be with a traditional KBC, so I'm assuming these functions are integral to the mini-KBC

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