Firmware, SCM F1

The latest release of this Firmware is detailed in the table below.

NameSmall Computer Monitor
ConfigurationF1
Release date 2019-06-02
Download ROM imageSCM F1 2019-06-02
Download source codeSCW 2019-06-03
Device Programming:
Code size32k bytes
Checksum (MiniPro 6.6)005C F912
Recommended ICAT27C256R-45PU
Core Components:
MonitorVersion 1.0.2
BIOSZ50Bus 1.0.1
Included Apps:
– ROM BASICVersion 4.7b.1
– CP/M loader from CF cardVersion 1.0

The ROM image is supplied (above) as an Intel HEX format file, which is suitable for use by most PROM programmers. Intel HEX files are a text format, not a binary format. As a result they are larger than the stated code size in the table above.

Source code is supplied (above) complete with the Small Computer Workshop development environment for Windows.

The Small Computer Monitor’s Components and Apps are described here.

Diagnostic display

At reset, the 8 LEDs next to the power LED are used to display the results of the self-test diagnostics. Each LED should light for a fraction of a second and the test should end with all 8 LEDs being turned off. Failures are indicated as follows.

DisplayIssue
Light sequence repeats indefinitelyRAM test failed
LED bit 0 remains onSerial port test failed
No light sequenceCPU not running, or
output port failed

Supported Devices

  • Z80 CPU (eg. Z84C00xx)
  • SIO #1 at 0x80 (eg. Z84C42xx)
  • SIO #2 at 0x84 (eg. Z84C42xx)
  • CTC #1 at 0x88 (eg. Z84C30xx)
  • CTC #2 at 0x8C (eg. Z84C30xx)
  • Digital I/O at 0x52
  • Compact Flash at 0x10 for loading CP/M
  • Bit-bang serial port at 0x28
  • Status LED at 0x08

The lack of specific support does not exclude the use of other hardware. It just means the ROM does not do anything specific with it.

Supported Modules

  • Self-test status display:
    • Z50Bus, digital I/O module (at 0x52)

The lack of specific support does not exclude the use of other hardware. It just means the ROM does not do anything specific with it.

Release Notes

When used with the on-board bit-bang serial port, the Small Computer Monitor’s software timed idle events run very slowly. This is due to the time the processor spends handling the serial port. When a Z80 CTC is present, the timing of idle events is not dependent on software delays and therefore runs at the correct speed.

Homebrew 8-bit retro computing