A ROM monitor program for the Calculon/80 microcomputer that resides in ROM and is loaded to RAM at boot. It enables users to control the computer and to load programs from disk or serial device.
This is a work in progress. While most of the drivers are complete, the HDD driver and utility programs are yet to be implemented.
+--------------------------------------------------------------------------+
| ROM MONITOR ARCHITECTURE |
+------------+-------------------------------------------------------------+
| Libraries | Applications |
| | |
| +--------+ | +-------+ |
| | ASCII | | | SHELL | |
| +--------+ | +-------+ |
| +--------+ +-------------------------------------------------------------+
| | STRING | | Hardware Abstraction Layer |
| +--------+ | |
| +--------+ | +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +---------+ |
| | ANSI | | | MEM | | ISR | | CTC | | PIO | | VDP | | COM | | CONSOLE | |
| +--------+ | +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +---------+ |
+------------+-------------------------------------------------------------+
Addr Program Size (bytes)
------ --------------- ---------------
0x0030 Main Program 4k - 40
0x0000 Bootloader 40
Start addr Purpose
---------- -------
0xFFFF Stack Top
0xF000 Stack Bottom
0xE000 Main Program
0xDC00 BSS: Uninitialized Data
0x0000 Page Zero: ISR
Device I/O Addr
--------------------------------------- --------
Bank Switching Device 0x00
Output Port A 0x0C
Z80DART Data register 0x10
Z80DART Control register 0x11
IDE Host interface - Data 0x18
IDE Host interface - Error 0x19
IDE Host interface - Sector count 0x1A
IDE Host interface - Sector number 0x1B
IDE Host interface - Cyliner low 0x1C
IDE Host interface - Cyliner high 0x1D
IDE Host interface - Head/Device 0x1E
IDE Host interface - Status 0x1F
IDE Host interface - Command 0x1F
IDE Host interface, High 8-bit 0x20
CTC - Channel 0 0x28
CTC - Channel 1 0x29
CTC - Channel 2 0x2A
CTC - Channel 3 0x2B
The bootloader is the first program to be executed when the computer starts. Its purpose is to test the memory where the Main Program will be loaded and then copy the Main Program into RAM by doing the following:
- Disable interrupts
- Wait for reset line to stabilize
- Test high RAM (0xE000-0xFFFF)
- Copy Main Program from ROM (0x0030) to RAM (0xE000)
- Run Main Program from RAM
The bootloader isn't allowed to utilize any RAM or devices other than what is needed to test the memory and copy the Main Program. Due to this, the stack can not be used.
This is the program that will be run from RAM once loaded from the ROM by the bootloader. Its purpose is to initialize all the device drivers, install interrupt service routines and start the shell program which is a part of the main program.
The program can be divided into four parts:
- Shell
- Utility Programs
- Libraries
- Hardware Abstraction Layer (Drivers)
The shell is the part the user interact with. It runs on top of the hardware drivers and lets users run commands.
A collection of useful programs for controlling the computer. The user can run them from the shell.
The libraries are a set of functions for string handling etc.
The hardware abstraction layer consists of device drivers which acts like the BIOS in CP/M and MS-DOS, except that they are invoked as subroutines instead of system calls (using interrupts or jump tables). The idea is to re-use these drivers when writing a DOS and to adapt them to allow system calls etc.
COM_INIT, COM_STATUS, COM_READ, COM_WRITE, COM_TX_OFF, COM_TX_ON
Subroutines for installing interrupt service routines.
ISR_INIT, ISR_INSTALL
CTC_INIT, CTC_ENABLE_INT, CTC_DISABLE_INT, CTC_SET_VAL
PIO_INIT, PIO_READ, PIO_WRITE
MEM_TEST, MEM_ROM_IN, MEM_ROM_OUT, MEM_BANK_STATE
HDD_READ_STATUS, HDD_READ_ERR, HDD_IDENTIFY, HDD_EXEC_DIAG, HDD_RESET, HDD_FORMAT_TRACK,
HDD_RECALIBRATE, HDD_READ_SECTOR, HDD_WRITE_SECTOR
This is a pseudo device driver that wraps a COM channel to allow buffered input and output as well as a more user friendly user interaction. It abstracts the console and does not necessarily need to utilize the COM driver for this, if a graphics device and keyboard is available, it could be used instead.
CONS_WRITE_CHAR, CONS_READ_CHAR, CONS_READ_LINE_ECHO, CONS_WRITE_STRING, CONS_ISR, CONS_MAIN