Consequence of changing DS1302 RTC to non-standard addresses

[Bill Shen]

The standard addresses for DS1302 RTC are 0xC0 for Z80 and 0x0C for Z180.  Because VGARC takes up 16 I/O addresses from 0x0 to 0xF, it interferes with RTC at 0x0C when operating in Z180 environment.  On my Z180 hardware I've changed RTC address to 0x1C and modified RomWBW configuration file changing RTCIO to 0x1C.  The modified RTC is operating well with VGARC in RomWBW environment, but I've noticed the CP/M program RTC.COM is not working.  It is easy enough to update RTC.COM with new address, but I'm wondering whether I'm also causing other problems somewhere else?
  Bill

[Wayne Warthen]

The RTC.COM application is very old and talks to the RTC directly (not through RomWBW HBIOS).  It assumes the RTC address based on the platform.  So, unfortunately, it won't recognize the RomWBW configuration change you made.  As far as I know, everything else accesses the RTC properly through the RomWBW HBIOS and should work fine.

Thanks,

Wayne

[Bill Shen]

Wayne,

Thank you for that answer which is what I’ve hoped for.  Relocating RTC to 0x1C resolved the conflicts with VGARC so now all my three new ROMless RomWBW boards have VGA and PS2 keyboard capabilities.  I didn’t expect the 36.8Mhz Z1RCC to work with VGARC over a backplane, but I’m pleasantly surprised.

  Bill

[Alan Cox]

0x18-0x1F has at various points been put down as "second IDE CF" but
I'm not aware of anything that has actually used or supported it and
in fact with the standard partial decode CF it would trample 0x98-0x9F
and break the TMS9918A if you did.

The other collisions for standard RC2014 style devices are
00 - GPIO
01/02 Joysticks
0C-0F MG014 printer port



Alan