Apple II Computer Info
Michael Foegelle
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kery
Subject: Re: Need info re accessing serial card
Organization: Griffin Software Development
Date: Sun, 31 Jul 1994 21:43:18 GMT
Lines: 145
| or disable the interrupts. I am not familiar with the ACIA used on the
| SSC, although I have programmed the 6850 ACIA several times, which
| allows the CPU to tell it to enable/disable all types of interrupts,
| rather than just the transmit/receive interrupts. If I leave the
| SSC interrupt switch turned on, and I turn the modem power on/off
| while running non-interrupt-aware software, the computer crashes. The
| CCS 7710 serial card used the 6850 ACIA and so it didn't have this problem,
| but unfortunately it uses DIP switches to set the bit rate.
|
| Does anyone know of a different serial card which both allows software
| control of the bit rate AND software control of interrupt enable/disable?
I always thought that the DIP switch on the SSC was similar to the power
bar concept for your computer: It doesn't prevent you enabling interrupts
through software when it is OFF (power bar OFF, computer ON), but it also
doesn't force you to enable interrupts when it is ON (power bar ON,
computer OFF). Someone please correct me if this is not the case.
Hmmm... I don't see the problem why everyone is so concerned about
unlikely (or impossible) interrupts. Consider:
The 6551 is only generating interrupts during the following situations when
both receipt and transmission interrupts are enabled:
o receipt register full
o transmission register full
o DCD state change
o DSR state change
The first two can be explicitly disabled on the 6551 through software.
The third one will only occur if you are online and your host hangs up on
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 487 of 572
(22 pages)
(16 pages)
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