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Re: [N8VEM: 7412] CP/M with 1.44M floppies

John,

Good work on the 1.44 interrupt driver.

John/Dan/Andrew/other BIOS hackers,
I have some reservations on the current state of the CBIOS. There large sections of code which are specific to the VDU and others specific to the DSKY. The VDU is integrated as an alternative console system. Shoudn't the DSKY be done in the same manner if I understand its use)? Then the debugging routines currently specific to the DSKY could be generic to the console driver selected. This would allow the community to be better able to test the code. 

Bill

John Coffman wrote:

Max,
The existing SBC makes a WatchDog Timer nearly impossible, as you observe. One needs an interrupt controller to handle interrupts from multiple sources. Then one wants to use IM 2 to do the fastest vectoring possible. I do think a WDT is possible -- and a good programming challenge. 

--John







On 07/05/2010 07:14 PM, Max Scane wrote:

Interesting, I don't think you would be able to setup an WDT under cp/m.
Generally the WDT relies on being pinged on a regular basis which is often part of a processing loop. About the only loop that would exist in cp/m would be the console input loop as part of the CCP. An application running under cp/m would also need to tap the WDT fairly regularly.
I guess you could do it via a regular interrupt but that would probably defeat the purpose. You could be in a tight loop (say looping on a status bit) but still responding to interrupts. Maybe the interrupt routine could check cpu state but I think it would still be very tricky. 

Cheers!

Max
On Tue, Jul 6, 2010 at 11:28 AM, Andrew Lynch <lyn...@yahoo.com <mailto:lyn...@yahoo.com>> wrote: 

    Hi John! Thanks! Excellent write up BTW! Awesome!

    Agree 100% on the WDT. It is long overdue and an essential part
    of any system.

    Would the Zilog Peripherals work as a watchdog timer? Set the CTC
    to count down from some number and then issue INT or NMI?

    If you are just using the straight interrupt mode without /WAIT
    then it might work. If you want a ZP I�ll send you one for test.

    Thanks and have a nice day!

    Andrew Lynch

    ------------------------------------------------------------------------

    *From:* n8...@googlegroups.com <mailto:n8...@googlegroups.com>
    [mailto:n8...@googlegroups.com <mailto:n8...@googlegroups.com>]
    *On Behalf Of *John Coffman
    *Sent:* Monday, July 05, 2010 9:02 PM
    *To:* n8...@googlegroups.com <mailto:n8...@googlegroups.com>
    *Subject:* Re: [N8VEM: 7407] CP/M with 1.44M floppies

    There is one goof in the write-up. My face is red!!!

    An existing CP/M cannot boot this new version; you must burn a
    ROM. The reason is the existing system will not run with the
    interrupt jumper ON, and the 1.44M support will not run with the
    jumper OFF. Dumb me, got caught last week, and forgot by the time
    I did the write-up this morning.

    Remember, the posted code is BETA. Good error recovery is still
    needed. Generally, though, I only get a fatal error when I get
    the floppy densities mixed up. The wrong density in the drive at
    the wrong time will cause a hang. The best way out of this
    situation: we need a watchdog timer in the N8VEM somewhere.

    --John





    On 07/05/2010 03:41 PM, Sergio Gimenez wrote:

    Thanks John !!

    Regards.

    Sergio.

    2010/7/5 John Coffman <john...@gmail.com
    <mailto:john...@gmail.com>>

    I've just posted in the BIOS Sync folder the source code and tools to
    make a version of CP/M with support for 1.44M 3.5" floppies. This
    code should be considered a beta test. A couple of new batch files
    are also included, one to create a new CP/M blank disk, and
    another to
    write a boot image to a floppy.

    --John

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