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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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8th Aug 2020, 4:25 pm | #121 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
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Re: SC/MP timing and microcode information
On another aspect of SC/MP behaviour, has anyone EVER used a jump instruction that used a displacement from P1, P2 or P3? Is this useful for anything?
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8th Aug 2020, 6:13 pm | #122 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Re: SC/MP timing and microcode information
Thanks for the NENIN pointers - that sounds about right though I'm wondering if NENIN is sampled at a clock edge to restart the cycle or just latched somehow. It being fed straight to the bus buffers sounds plausible and would make sens. I'll have to rig something up to try some really short pulses on NENIN to find out how it is latched or registered.
I was wondering about how calls into other pages are usually done. Is it usually with a XPPC? I suppose the pointer relative jumps would be a nice way to do a vtable for object oriented code? |
8th Aug 2020, 6:29 pm | #123 | ||
Octode
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,363
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Re: SC/MP timing and microcode information
Quote:
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8th Aug 2020, 6:57 pm | #124 |
Octode
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,287
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Re: SC/MP timing and microcode information
I'm currently designing a logic simulator that calculates timings so any info on the timing relationship between XOUT and transitions on NADS, NRDS, NWDS etc would help with making a waveform generator for SC/MP processors..... The data sheets are suspiciously vague on this as I believe you noted before.
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8th Aug 2020, 7:16 pm | #125 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,294
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Re: SC/MP timing and microcode information
From figure 4 of the datasheet it looks like NENOUT low indicates the cycle has been completed. But there seems to be no specific hold time between NENIN and NENOUT.
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15th Aug 2020, 5:12 pm | #126 | |
Pentode
Join Date: Jun 2012
Location: Bristol, UK.
Posts: 115
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Re: SC/MP timing and microcode information
Quote:
Yes, you can make a big jump within the current page. Or, you can jump (NS say 'transfer control') to ANOTHER page. |
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