Re: cbm8032 crashing at end of tape load...

From: Greg King <>
Date: Sat, 05 Nov 2016 20:57:44 -0400
Message-id: <>
On 2016-11-05 10:51 AM, didier derny wrote:
> Thanks for the information; I'll have to check those signals.
> I guess the signal leaving the 6545 is OK; or, I would have a bad display.
> Everything looks like if there was another source of irq above the one
> from the crtc.
> The cursor looks mostly good; but some times, a kind of high-speed blinking.
> On 05/11/2016 12:50, Christian Dirks wrote:
>> I think /IRQ is generated by the 6520 on UB12 by VERT DRIVE on CB1,
>> coming from the CRTC through the 7486 on UC2.
>> Am 04.11.2016 um 21:46 schrieb didier derny:
>>> Now, the cbm8032 is powered with 12v DC, with 2 diodes added on the
>>> circuit to drop the 12v to about 10.8v (9.3v on unregulated connector).
>>> When I check the 6v on the tape connector, it is at about 6.05v, seems
>>> correct.
>>> When I try to save a program, everything looks OK.
>>> When I try to load a program, seems OK to the "Ready."; but, no cursor --
>>> any idea?
>>> I may have a clue: the cursor blinking seems irregular.  I guess a
>>> problem with the irq.
>>> Any idea how the irq is generated on the 8032?  6522?

The CRTC makes the "Jiffy" interrupt.  The datasette driver disables 
that one, and uses its own higher-rate timer interrupt.  When it 
finishes, it disables its interrupt, and re-enables the Jiffy one.

But, it looks as though the datasette IRQ isn't being disabled on your 
machine, after a LOAD.

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Received on 2016-11-06 01:00:02

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