PDP-11/10 repair started
ard at p850ug1.demon.co.uk
Mon Oct 5 00:22:01 CDT 2015
> > The other is the 11/05S schematic, which shows the later boards with
> > the crystal UART clock
> Say what? The "11/05S schematic" from Bitsavers shows the RC clock; look on
> page 61, bottom left corner, there's an RC circuit (and a couple of flops)
> producing an output "DPH TTY CLK (I) H", which is fed into the baud rate
> divider in the upper left corner.
Yes, you're right. I am not sure what I was thinking of last night.... But isn't
the switchable divider only present on later boards (the early ones being
pretty much 110 baud only)?
This printset _does_ show the jumpers I mentioned. Look at page 75 of the
.pdf bottom, left-ish. Jumper W1 is described as disabling the internal serial
port when fitted. On the next page, just above leftish of centre is W2,
documented as installed to make a slave processor.
> (Ooooh, what an ugly circuit! You have to tweak the trim pot to change from
> the 110/220/440/880/1760 speed set to the 150/300/600/1200/2400! Ugly!!)
May be easier than finding the right crystal to change a DL11A-E to the
'other' set of baud rates :-)
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