KOMODO Monitor Program V1.0.0

Software component of the single board computer design using a M68000 CPU. Hardware designs can be found in the mcd-pcb repo.

Planned Expansion

• Save last loaded program start location, use with GO when no arguments
• Save list of user loaded programs
• Split into separate files with INCLUDE pre-processor directive
• Use hardware UART echo mode (loopback)
• Use UART interrupt mode instead of polling
• Memory management

Program memory Structure

Address	Purpose
ROM
00_0000	Exception Vector table
00_8000	Monitor program start
00_88CA	Command table start
00_891E	String Constant storage
RAM
01_0000	Program Data. Global variables & line buffer
01_1000	Recommended user program locations
01_FFF0	System Stack start. Fills up from bottom
DEVICE
02_000	Serial device start (odd addresses only)

Many subroutines set flags in D7 to indicate error

D7 Bit	Flag
0	invalid hex input
1	invalid hex parameter
2	S-Record checksum error

TRAP #0

Used to terminate programs running in user mode. Use like C's return from main() or exit().

TRAP #15

System Calls available with TRAP #15

Put task number in D0.B

Task	Usage
0	Print the byte in D1.B
1	Print the word in D1.W
2	Print Lowest 6 bytes in D1
3	Print the longword in D1.L
4	Print newline
5	Read single ascii character into D1.B
6	Display single ascii character in D1.B
7	Read a hex character into D1. All input routines set D7 bit 0 (LSB) on conversion error
8	Read a hex byte into D1.B
9	Read a hex word into D1.W
10	Read a longword into D1.L
11	Toggle input upper case conversion. D1.B=0 (disable), !=0 (enable, default)
12	Toggle keyboard echo. D1.B=0 (disable), !=0 (enabled, default)
13	Display Null terminated string at A1 with trailing CR,LF
14	Display Null terminated string at A1

Full Hardware Memory Map

References

Clements, A. (1997) Microprocessor Systems Design: 68000 hardware, software, and interfacing. PWS Publishing Company.