Re: BZ AVG progress

Well the basic idea of the State machine (And I may be re-hashing stuff you already
know) is that the strobe's and latches control everything of course. The latches involve
putting the data from the VGRAM or VGROM into the correct Vector XY Address.
The strobes basically enable 'actions' of the state machine. Most of these actions come
down to an AND or NAND gate to enable that fuction. the important thing to remember is
that a particular strobe does not have only one action. If you look at the sheet you
retyped from my .pdf doc, you will notice that the same strobe does different things based
on which opcode it is triggered on. That is why you will see lots of AND/NAND gates around
the state machine (I don't have my schems in front of me again) that have one strobe as an
input and one opcode line (OP0-OP2).
  since you know that the Center command is not working. First figure out which strobe is
used to invoke the center command (strobe 3).. Ahhh, looks like strobe 3 also triggers the
HALT and the VCTR command. Maybe your logic problem is HALTing the VG instead of centering
it?

function opcode op2-op1-op0
  HALT 1 001
  VCTR 0,2 000,010
 CENTER 4 100

So, you can follow the logic now....

 The LS02 at N9... OP2 and Strobe3.... So, the center command is only started when
strobe 3 is low and op2 is high.

 LS27 at N7... OP2 & OP0... the Vector Draw command is only started when strobe 3
is low and OP2 | OP0 are low as well.

 LS74 at M9... OP0 ... Halt is invoked when strobe 3 is low and OP0 is high.

You should be able to check the outputs of each of these 'sections so see what is exactly
happening that is incorrect when the state machine should be 'centering'.

Keep us posted.... :-)
 

> David Shoemaker wrote:
>
> I have now determined that my AVG is only partially brain dead.
>
> Jump
> Halt
> Stat
> Scale
> short draw
>
> All work, Center for sure doesn't work. The AVG hangs at the first byte of the next
> command following the center.
>
> Still not grocking quite enough to figure out just what is up.
>
> Ideas welcome.
>
> David
>
>
Received on Thu Aug 26 09:46:57 1999