23 Sep
2011
23 Sep
'11
6:12 a.m.
On Thu, 22 Sep 2011, Tony Duell wrote:
You were lucky. In one device I was working on
recently, the microcode
Well, this particular ROM can be placed either in E1 (RK05J) or E2
(RK05F).
I am sprised they used a ROM for that. Is the enable
input used -- is there
some other open-colelctor output tied to the outputs of this ROM? If not,
you could do it i na copuple of TTL pacakges I think.
There are four ROMs on this board, they are used because this board can be
used in either a RK05J or RK05F (twice the number of cylinders). They use
the enable input as some kind of "seek enable" (called difference enable),
and the outputs are forced low with SN7416 drivers when the difference is
greater than 31 cylinders. The "value" from the ROM only determines the
seek speed profile, i.e. how fast the positioner will move the carriage.
Do you know that it simply inverts the signals, or
could it do soemthing
differnt for small cylinder offsets?
According to the schematics and the contents that I've read out of the ROM
it's nothing more. At least the drive works fine with this assumption. But
I'll read out an intact ROM if I can find one on another card.
Christian