[N8VEM-S100:7461] Help me understand System Monitor Board.

[Todd Miller]

I have an early ver SMB.

I has worked fine for years in my Imsai displaying address & instruction.

Now that I have finished a mini ver of the Imsai, I want to use it there.
My problem is it will not display the instruction, i'ts always FF.

Looking at the board layout and schematics, Til311 DIS7 and DIS8 are the
for the Data display..

What I don't understand is they are strapped to B-D10-D17, shouldn't
they be hooked to B-D0-D7.

I look at it like this;

The Hex displays are on the buffered Data bus, to enable display; pin 5
of the Til311should be grounded. This is the same as latch_data_8*.

I tried grounding U10 pin 6, latch_data_8* with no results. Is it possible
one of the boards is asserting something to prevent a read from the bus ?

Time for a break....


Todd

[monahanz]

Todd, Its B-i0 to bi7 the S100 bus bit *input *lines. These are the
*output* upper 8 bits (of 16) for S100 bus 16 bit transfers. The direction
is pin 2-> to pin 18 etc. Only relevant on the mezzanine board for 16 bit
transfers.

Post by Todd Miller
I have an early ver SMB.
I has worked fine for years in my Imsai displaying address & instruction.
Now that I have finished a mini ver of the Imsai, I want to use it there.
My problem is it will not display the instruction, i'ts always FF.
Looking at the board layout and schematics, Til311 DIS7 and DIS8 are the
for the Data display..
What I don't understand is they are strapped to B-D10-D17, shouldn't
they be hooked to B-D0-D7.
I look at it like this;
The Hex displays are on the buffered Data bus, to enable display; pin 5
of the Til311should be grounded. This is the same as latch_data_8*.
I tried grounding U10 pin 6, latch_data_8* with no results. Is it possible
one of the boards is asserting something to prevent a read from the bus ?
Time for a break....
Todd