P112 ROM Monitor

The P112 board has a 32K flash ROM chip that contains the startup initialization code and a small monitor-debugger.

There are two known versions of the ROM code: the original one from Dave Brooks and an enhanced version from Harold Bower. The last one adds support for more floppy formats, SCSI and IDE interfaces, includes commands for setting and displaying the Time-of-Day, and saves the configuration parameters in the Non-Volatile RAM.

I use the H. Bower's version of the ROM monitor since it is more versatlie. I've made the following modifications:

  • The memory sizing algorithm is now non-destructive, in order to preserve RAM-disk contents between resets (see the CP/M 2.2 BIOS with RAM disk).
  • The GIDE boot code now recognizes "standard" boot sectors. Originally, the enhanced ROM monitor would recognize only the "new" (B/P-type) boot sectors when booting from an IDE hard disk (see also the fdisk program).
  • Corrected a bug in the clock support routines that caused the monitor to display garbage when the clock chip contained an invalid month.
  • The Z80182 register setup is now done in the correct order. Before, trying to do a sofware reset of the P112 board caused the machine to hang.

Recently, an updated ROM (version 5.0) has been made available by Terry Gulczynski, which implements hardware flow control for the main serial port and a new debugger command. I've merged both my changes and Terry changes into a new version (5.1). You can find it in the download area, together with older versions. All packages include sources and ROM images in Intel HEX format. Version 4.3 and up come with Tiny BASIC in a separate HEX file.

Last updated: 8-Feb-2006.