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

Name	Small Computer Monitor
Configuration	F2
Release date	2022-10-16
Download ROM image	SCM F2 2022-10-16
Download source code	SCW 2022-10-16
Device Programming:
Code size	32k bytes
Checksum (MiniPro 6.6)	01DA 047A (SST39SF010A)
Recommended ICs	SST39SF010A AT27C256R-45PU
Core Components:
Monitor	Version 1.3.1
BIOS	SCZ80 1.3.1
Included Apps:
– ROM BASIC	Version 4.7b.1
– CP/M loader from CF card	Version 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.

Display	Issue
Light sequence repeats indefinitely	RAM test failed
LED bit 0 remains on	Serial port test failed
No light sequence	CPU not running, or output port failed

Supported Devices

• Z80 CPU (eg. Z84C00xx)
• SIO #1 at 0x80 (eg. Z84C4xxx)
• SIO #2 at 0x84 (eg. Z84C4xxx)
• CTC #1 at 0x88 (eg. Z84C30xx)
• CTC #2 at 0x8C (eg. Z84C30xx)
• ACIA #1 at 0xA2 (eg. 68B50)
• ACIA #2 at 0xA4 (eg. 68B50)
• CF Card at 0x90 for loading CP/M
• Diagnostic LEDs and digital I/O at 0xA0
• 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 Cards

This configuration for SCM can be used with SC516 but the onboard bit-bang serial port is not supported.

• Processor:
  • SC518, Z80 Processor card for Z50Bus
  • SC516, Z80 Processor card for Z50Bus *

• Memory:
  • SC519, Z80 Memory card for Z50Bus
  • SC516, Z80 Processor card for Z50Bus *

• Serial port:
  • SC511, Serial and timer card for Z50Bus (Z80 SIO & CTC)
  • SC520, Serial ACIA 68B50 card for Z50Bus
  • SC521, Serial Z80 SIO/2 card for Z50Bus
  • SC125, Serial and timer card for Z50Bus (Z80 SIO & CTC)

• Timer:
  • SC511, Serial and timer card for Z50Bus (Z80 SIO & CTC)
  • SC514, Z80 Counter/timer card for Z50Bus (Z80 CTC)
  • SC125, Serial and timer card for Z50Bus (Z80 SIO & CTC)

• Baud rate generation:
  • SC511, Serial and timer card for Z50Bus (Z80 SIO & CTC)
  • SC514, Z80 Counter/timer card for Z50Bus (Z80 CTC)
  • SC125, Serial and timer card for Z50Bus (Z80 SIO & CTC)

• CP/M storage:
  • SC504, Compact Flash interface for Z50Bus (at 0x90)
  • SC127, Compact Flash interface for Z50Bus (at 0x90)

• Self-test status display:
  • SC506, Digital I/O card for Z50Bus (at 0xA0)
  • Z50Bus, Digital I/O module (at 0xA0)

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 using a 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.

Older Releases

Name	Small Computer Monitor
Configuration	F2
Release date	2022-02-27
Download ROM image	SCM F2 2022-02-27
Download source code	SCW 2022-03-01
Device Programming:
Code size	32k bytes
Checksum (MiniPro 6.6)	01DA 2902 (SST39SF010A)
Recommended ICs	SST39SF010A AT27C256R-45PU
Core Components:
Monitor	Version 1.3.0
BIOS	SCZ80 1.3.0
Included Apps:
– ROM BASIC	Version 4.7b.1
– CP/M loader from CF card	Version 1.0