The latest release of this Firmware is detailed in the table below.
Name | Small Computer Monitor |
Configuration | S3 |
Release | 2022-02-27 |
Download | SCM S3 2022-02-27 (HEX) |
Device Programming: | |
Code size | 32k bytes |
Checksum (MiniPro 6.6) | 005B 1AD2 (AT27C256R) 01D9 9AD2 (SST39SF010A) |
Recommended IC | AT27C256R-45PU (32kB) SST39SF010A (128kB) |
Core Components: | |
Monitor | Version 1.3.0 |
BIOS | SCZ80 1.3.0 |
Included Apps: | |
– ROM BASIC | Version 4.7.1 |
– 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 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) [rc addressing]
- SIO #1 at 0x80 (eg. Z84C4xxx) [zilog addressing]
- SIO #2 at 0x84 (eg. Z84C4xxx) [rc addressing]
- SIO #2 at 0x84 (eg. Z84C4xxx) [zilog addressing]
- 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, plus:
- RC2014, Z80 CPU (Classic/2 kit), plus:
- RC2014, clock module (Classic/2 kit)
- SC108, Z80 CPU, RAM, ROM and clock module
- Memory:
- RC2014, memory module pair:
- SC108, Z80 CPU, RAM, ROM and clock module
- SC143, ROM module, plus
- RC2014, 32k RAM module (Classic/2 kit)
- Serial port:
- RC2014, serial module (68B50 ACIA) – retired
- RC2014, serial module, 68B50 ACIA (Classic 2 kit)
- RC2014, dual serial module (Z80 SIO/2)
- Karl’s #61, serial and storage (ACIA & CF)
- Baud rate generation:
- 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
- others
- Self-test status display:
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.