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Re: Question ISA BUS clock [message #6202 is a reply to message #6201]

Tue, 02 April 2019 01:31

Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR

Senior Member

Well, to make an RTC work in DOS you don't really need a BIOS extension. You'll need a clock device driver. It must be an example of that somewhere in the Interwebs.

Regarding microcontroller to PC interfacing, there are a few options:
1. Add a wait logic that would insert enough wait states for the microcontroller to input or output the data
2. Use some kind of FIFO, e.g. CY7C421, a bit of an overkill probably.
3. Add input/output flip-flops and buffers. E.g. use a 74*273 for storing the ND address or command/data that is written to the microcontroller. Use 74*244 for reading the data. 74*273 and 74*244 would be enabled by /CS AND /IORD, and /CS AND /IOWR respectively. If needed, the delays can be implemented in the software/driver.

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[Message index]

		Question ISA BUS clock By: 32768 on Fri, 29 March 2019 00:20
		Re: Question ISA BUS clock By: monahan on Sat, 30 March 2019 08:15
		Re: Question ISA BUS clock By: 32768 on Sun, 31 March 2019 08:46
		Re: Question ISA BUS clock By: Andrew B on Sun, 31 March 2019 12:51
		Re: Question ISA BUS clock By: Sergey on Mon, 01 April 2019 12:01
		Re: Question ISA BUS clock By: 32768 on Tue, 02 April 2019 00:07
		Re: Question ISA BUS clock By: Sergey on Tue, 02 April 2019 01:31
		Re: Question ISA BUS clock By: 32768 on Sun, 07 April 2019 22:48
		Re: Question ISA BUS clock By: Sergey on Mon, 08 April 2019 16:33

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