The latest release of this Firmware is detailed in the table below.
Name | Small Computer Monitor |
Configuration | S5 |
Release | 2022-10-16 |
Download ROM image | SCM S5 2022-10-16 (HEX) |
Download source code | SCW 2022-10-16 |
Device Programming: | |
Code size | 32k bytes |
Checksum (MiniPro 6.6) | 07D2 E8FF (SST39SF040) |
Recommended IC | SST39SF040 |
Core Components: | |
Monitor | Version 1.3.1 |
BIOS | RC/Z180 1.3.1 (native) |
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 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
- Z180 CPU (eg. Z8S180xx) at 18.432 MHz
- Z180’s asynchronous serial ports
- Z180’s timer (for idle events)
- 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. Also, it needs a 7.3728 MHz clock source. Third-party modules often have address options and onboard clock sources to avoid these problems.
The official RC2014 SIO module does not have tight address decoding so it appears as an SIO at both 0x80 and 0x84. Also, it needs a 7.3728 MHz clock source.
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 and memory:
- Memory:
- Serial port:
- Timer:
- Baud rate generation:
- CP/M storage:
- Self-test status display:
- RC2014, digital I/O module
- SC129, digital I/O module (eight LEDs)
- SC134, LED outputs for RC2014 (eight 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
The Z180’s internal I/O is set to the range 0xC0 to 0xFF.
Release History
Config | Date | Monitor | BIOS | Base I/O |
S5 | 2019-04-30 | S5.0.03 | Beta | 0x40 |
S5 | 2019-06-02 | 1.0.2 | 1.0.1 | 0x40 |
S5 | 2022-02-27 | 1.3.0 | 1.3.0 | 0xC0 |
S5 | 2022-10-16 | 1.3.1 | 1.3.1 | 0xC0 |
Older Releases
Release 2022-02-27
Name | Small Computer Monitor |
Configuration | S5 |
Release | 2022-02-27 |
Download ROM image | SCM S5 2022-02-27 (HEX) |
Download source code | SCW 2022-02-27 |
Device Programming: | |
Code size | 32k bytes |
Checksum (MiniPro 6.6) | 07D2 F77B (SST39SF040) |
Recommended IC | SST39SF040 |
Core Components: | |
Monitor | Version 1.3.0 |
BIOS | RC/Z180 1.3.0 (native) |
Included Apps: | |
– ROM BASIC | Version 4.7b.1 |
– CP/M loader from CF card | Version 1.0 |
Release 2019-06-02
Name | Small Computer Monitor |
Configuration | S5 |
Release | 2019-06-02 |
Download ROM image | SCM S5 2019-06-02 (HEX) |
Download source code | SCW 2019-06-02 |
Device Programming: | |
Code size | 32k bytes |
Checksum (MiniPro 6.6) | 07D6 357F (SST39SF040) |
Recommended IC | SST39SF040 |
Core Components: | |
Monitor | Version 1.0.2 |
BIOS | RC/Z180 1.0.1 (native) |
Included Apps: | |
– ROM BASIC | Version 4.7b.1 |
– CP/M loader from CF card | Version 1.0 |