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

Name	Small Computer Monitor
Configuration	S7
Release	2023-06-10
Download	SCM S7 2023-06-10 (HEX)
Device Programming:
Code size	32k bytes
Checksum (MiniPro 6.85)	07D2 DEBC (39SF040)
Recommended IC	SST39SF040
Core Components:
Monitor	SCM version 1.3.1
BIOS	SC/Z80 version 1.3.1
Included Apps:
– ROM BASIC	Version 4.7b.1
– CP/M loader from CF card	Version 1.0

The firmware 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.

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

Source code can be found in the Small Computer Workshop download.

Diagnostic and Status display

At reset, the system performs a self-test. The results are shown on the set of 8 diagnostic LEDs, if present, and the single status LED, if present.

Diagnostic LEDs: These should be off when the reset button is being pressed. Once released from reset, each LED should light in sequence for a fraction of a second and the test should end with all 8 LEDs being turned off. Failures are indicated as follows.

Diagnostic LED display	Issue
LEDs always off	CPU not running, or Output port failed, or Reset failure
LEDs always on	Output port failed
Light sequence repeats indefinitely	RAM test failed
Light sequence then LED bit 0 remains on	Serial port test 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 0x80 (eg. 68B50)
• ACIA #2 at 0x40 (eg. 68B50)
• CF Card at 0x10 for loading CP/M
• Diagnostic LEDs and digital I/O at 0x00

The SIO can either use the RC2014 addressing scheme or the typical Zilog scheme (as used by Dr. S. Baker’s SIO module)

The addresses of the official RC2014 SIO and ACIA modules clash, so they can’t both be installed at the same time. Third-party modules often have address options to avoid this problem.

The official RC2014 SIO module does not have tight address decoding so it appears as an SIO at both 0x80 and 0x84.

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

• Processor:
  • RC2014, Z80 CPU module
  • SC149, Z80 CPU module
  • SC706, Z80 CPU module
  • SC730, Z80 CPU + MMU module

• Memory:
  • SC714, Memory 512k FLASH ROM plus 512k RAM
  • SC720, Z80 SBC with 512k FLASH ROM plus 512k RAM
  • SC721, Memory 512k + 512k, when used with SC730

• Serial port:
  • RC2014, serial module, Classic 1 (68B50 ACIA) – retired
  • RC2014, serial module, Classic 2 (68B50 ACIA)
  • Karl’s #61, serial and storage (ACIA & CF)
  • SC104, serial module (Z80 SIO/2)
  • SC110, serial and timer module (Z80 SIO & CTC)
  • SC132, serial module (Z80 SIO/0)
  • SC139, serial module (68B50 ACIA)
  • SC705, serial module (68B50 ACIA)
  • SC716, serial module (Z80 SIO/2)
  • SC720, Z80 SBC with Z80 SIO/2 serial
  • and others

• Timer:
  • SC102, counter timer module (Z80 CTC)
  • SC110, serial and timer module (Z80 SIO & CTC)
  • SC718, counter timer module (Z80 CTC)

• Baud rate generation:
  • RC2014, dual clock module
  • SC102, counter timer module (Z80 CTC)
  • SC110, serial and timer module (Z80 SIO & CTC)

• CP/M storage:
  • RC2014, compact flash module
  • Karl’s #10, compact flash module
  • Karl’s #61, serial and storage (ACIA & CF)
  • Karl’s #72, compact flash module
  • Karl’s #73, compact flash module
  • SC145, compact flash interface module
  • SC715, compact flash interface module
  • SC720, Z80 SBC with compact flash storage
  • and others

• Self-test status display:
  • RC2014, digital I/O module (eight LEDs)
  • SC151, Paged ROM module (single status LED)
  • SC129, digital I/O module (sixteen LEDs)
  • SC134, LED outputs for RC2014 (eight LEDs)
  • SC719, digital I/O module (sixteen LEDs)
  • SC720, Z80 SBC with eight diagnostic LEDs)

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

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