ADV11-A vs. ADV11-C and 22-bit Bus

[Jerry Weiss]

> On Jan 27, 2018, at 11:16 AM, Mark Matlock via cctech <cctech at classiccmp.org> wrote:
> 
>   I have an ADV11-A that I would like to use in a Q22 RSX11M+ system. The ADV11-C will work in a 22-bit Bus system from what I understand but the ADV11-A was made for 18 bit Bus systems. In the OEM Micronote book, Note 5, it states:
> 
>    Any device which uses backplane pins BC1, BD1, BEl, BF1 or DC1, 001, DEl, OF!, for purposes other than BDAL18-21 is electrically incompatible with the 22-bit bus and may not be used without modification. 
> 
> 
>   Further down it lists the ADV11-A as a device that does not meet the requirements for a Qbus 22-bit system because:
>        ADV11 (A012).   A/D Converter. (Use of BC1 for purposes other than BDAL18)
> 
>   When I look at the Board connector B pin C side 1 (component side) the BC1 pin is tied to ground. Several other pins are also tied to ground on that connector such as BC2, BJ1, and BT1. Other than BC1 which is BDAL18 being tied to ground the pins BDAL19 (BD1), BDAL20 (BE1), And BDAL21 (BF1) are all not connected to anything. This also matches the field engineering print for ADV11-A (B-TC-ADBV11-A-1) where BC1 is shown tied to ground on page 21.
> 
>   So it looks like if I simply cut the trace between the BC1 finger and its connection to ground on the board it would become Q22 compatible.
> 
> Is it that simple?
> 

I am considering the same modification to my own ADV11-A.  I just located the field maintenance print you referenced, so I can now research this a bit further myself.

Being a interrupt only device and using on BBS7 to decode the IO page, this should function in an Q/Q backplane slot "in theory".   


Jerry
jsw at ieee.org