25 Nov
2015
25 Nov
'15
10:46 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 25 November 2015 17:10
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/25/2015 11:01 AM, Robert Jarratt wrote:
Ah, I misread your earlier response, I thought you were saying something different.
Regards
Rob
My reading of the Qbus spec is that P OK and DC
OK are active high.
That diagram tells me that both control signals are driven the same
way because the two circuits are identical except for the timing caps.
When the power is OK the output of the inverters is low, so the
transistors are off, presumably allowing the signals to float high.
When the power is not OK, the inverters are high, turning on the
transistors and shorting the signal to ground. But, I am no expert,
and could have interpreted those circuits all wrong. Regards Rob
Yup, I read the
circuit the same way.