On (24 Jan 95) [EMAIL PROTECTED] wrote...
> From: Simon Cooke <[EMAIL PROTECTED]>
> Date: Tue, 24 Jan 1995 12:49:45 +0000 (GMT)
> I'll check with Martin... it may be the same mod and I'm getting mixed
> up, but it didn't work before we did it, and only worked when we had
> restored the cut track *and* had the diode in place as you describe as
> well... How odd..
What's the problem Si? have you got a new comms-int that needed patching but
all didn't go to plan or somthing?
> *grins* Don't you just love it. I wish that Bruce had just done the ASIC
> and everyone else had mulled around on the board -- the sam would have
> been released much earlier and perhaps would have been less buggy in
> these respects -- no disrespect to bruce there though.
I agree, but that would've held back the launch and their creditiors would've
probably called in the debt before the Sam ever made it into the world:-(
Though Appart from the lack of 8MHz clock signal to the FDC chips and no CPU
clock during ASIC reset what are the other problems with the mother-board?
I havn't noticed anything else!
> Funny you should mention this -- last night I connected the SAM to the PC
> and saw what happened -- lost chars all over the place due to the PC's
> dodgy hardware flow control. All I can say is... What a chip the IM26C91
> is!
I think all the hardware flow-control on PeeCee's is emulated in software and
that the 8250 & 16550 operate in DUMB mode ie they'll send chars regardless of
the other ends CTS status! As such they tend to be at least 1character late at
halting the Tx stream and with the Fifo'd 16550 it probably continues to send
until its 16byte Tx-fifo is emptied!
I know that some Interupt driven UART drivers on PeeCee's actually drop RTS
when the interupt buffer is only 3/4ths full to make sure the sender has enough
space to over-run it's RTS signalling! And only releases RTS when the buffer
get's to the half-full level!
Though the 26C9x chips arn't perfect as propgation delay over a few meters at
115200 baud would cause the automatic flow-control to arrive at the transmitter
too late to stop the next char... but it's certainly better than any xxx50
UART's:-)
Note you can get 2692 & 2694 chips that contain 2 & 4 of these UART's!
I have the data of the dual UART version and it adds an Extra function that
can implement a Rx Time-out interupt function for all those transfer protocols
etc... One could program a background file transfer function that runs totally
on the UART interupts!
> If the above works then it might allow SAM to receive at 115200baud I
> mentioned in a previous message about commix;-)
> Hmmmmm........
That got you thinking eh? <Grin> Ever get the feeling that I like to keep
the odd little suprise up my sleeve to spice things up every now and then?
> If only /my/ SAM (as opposed to Martin's) had a working keyboard and a
> working drive. I don't want one of the dodgy ones from West Coast though...
Get a cheap PC keyboard and strip it down.... then re-wire the switch-matrix
to match the SAM keyboard, and re-label the keys that don't match up!
As to the Floppies... Well Si, you *could* take your broken internal drive
and remove the fdc pcb...
knock up a simple converter pcb that can then be plugged into a normal External
3.5" drive via a normal 34way ribbon, all the control lines are there and
there's also +5V & 0V for lines that need to be pulled up or down...
Just in case you or anyone else tries this... Use the /MOTOR line as both the
floppies /MOTOR line AND the /Drive-select line. Much tidier than the external
FDC's tying the floppies /drive-select perminantly low which leaves the drive
LED on all the time!
I havn't done this adaption, but I think I will in the near future to free up
another external bus-slot;-)
> Actually, we're trying to get the High Density drive working soon...
> we've made the PCB for the SAM Hard Drive (v0.2) now, and we'll post
> laser-printed acetates to you (jonathan) as well as a guide to what
> chip's where) in the near future...
Me? 'h' missing again, it's Johnathan;-)
^
> I assume that you /can/ photoetch pcbs? :)
Not at the Mo' but rest assured it wouldn't take me long to get the gear;-)
Cheers!
I'll probably have 99% of required components here already on numorous old
PCB's;-) and I've got 6 x 64way EuroPlugs too! So the only things I expect I'll
need to buy would be the photo-resist coated copper-clad boards and the IDE
plug and leads(got an old UV Suntan lamp somwhere that'll do the UV exposure;-)
regards
Johnathan.
... Teamwork is essential it allows you to blame someone else
--
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