On 04/30/2018 07:51 PM, Mia Magnusson wrote: > Den Mon, 30 Apr 2018 19:08:59 +0200 skrev Francesco Messineo > <francesco.messineo@gmail.com>: >> On Mon, Apr 30, 2018 at 7:05 PM, Mia Magnusson <mia@plea.se> wrote: >>> Den Mon, 30 Apr 2018 15:00:41 +0200 skrev Michał Pleban >>> <lists@michau.name>: >>>> Hello! >>>> >>>> Mia Magnusson wrote: >>>> >>>>> My intention is to find some kind of suitable software for timing >>>>> diagrams (I was first thinking about project management software, >>>>> but there seems to be software especially made for thins >>>>> purpose). >>>> >>>> Why not simply attaching a logic analyzer to various signals and >>>> measure what the real hardware does? >>> >>> Everything is made of standard 74xx circuits and standard DRAM's >>> (except the CPU and the CRTC) and it would be really nice to know >>> that the maximum and minimum delays is for each part of the >>> circuit. (The 6525's doesen't count in this discussion as their >>> timing isn't critical to understanding how the complicated >>> CPU-RAM-Refresh-Coprocessor stuff works). >>> >>> I wounder if anyone who designed or in general worked with the >>> hardware on theese machines at Commodore are still alive and >>> remembers some stuff? For example it would be nice to know why some >>> signals are called PUP1 and PUP2. >> >> look if they're static pulled up to some resistor to Vcc... PullUP1, >> PullUP2... Just guessing, but I use a similar naming scheme when I >> design my own boards. > > Thanks! Yes, they seem to go to pull-up resistors. > > But why not just join each of those TTL inputs with +5V directly on the > nearby chip? > > Does some 74xx IC's work better with slightly less drive to +5V on the > signal that feeds the inputs? I don't remember where, but I read somewhere, that you shouldn't connect a TTL input directly to +5V. GerritReceived on 2018-04-30 21:00:02
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