This repository contains a version Steve Wozniak's ROM monitor for the 6502, ported to the Rockwell R6501 and R6511 single-chip microprocessors. These processors are 6502-like, but contain some significant differences:
- Zero page is internal to the processor, and smaller than 256 bytes
- I/O devices in zero page
- Hardware stack in zero page, of limited size
eWoz provides the ability to examine memory, deposit memory, jump to an address, and to load Intel HEX data. The following is a somewhat brief overview of the monitor's operation. For more details on combinations possible with the basic examine/deposit/jump commands, see this SB-Projects writeup.
Note that the escape/cancel character for this version of eWoz is CTRL+C (Control-C). It can be typed at most points during most operations and will soft reset eWoz.
Examining a single memory location is done by typing the address and pressing enter:
0200
0200: 8A
You can omit the leading zeros:
200
0200: 8A
Several addresses can be specified on a single line:
200 211 222 233
0200: 8A
0211: 44
0222: 35
0233: 30
You can also examine a range of memory:
0200.02FF
0200: 8A B7 B0 B0 B0 D2 8D 30 30 31 46 46 0D 32 35 31
0210: 30 44 30 41 30 30 30 30 37 30 30 30 37 30 31 30
0220: 37 32 35 44 0D 38 36 35 36 33 36 42 37 33 37 35
0230: 36 44 32 30 36 35 37 32 37 32 36 46 37 32 32 45
0240: 30 44 30 41 30 30 30 44 30 41 34 42 0D FF FF FF
0250: FF FF FF FF FF 8D FF FF FF FF FF FF FF FF EF FF
0260: FF FF FF FF FF EF FF FF FF FF FF EF FF FF FF FF
0270: FF FF FF FF FF FF FF FF FF FF FF FF EF FF FF FF
0280: 20 89 04 40 00 80 02 10 40 00 00 01 00 80 00 04
0290: 02 41 C8 00 00 00 20 40 10 00 00 02 00 00 02 12
02A0: 40 00 00 08 00 00 00 12 00 20 00 00 40 01 00 00
02B0: 10 80 00 04 00 00 00 00 00 01 00 00 00 00 00 00
02C0: 20 14 21 10 00 00 00 00 00 00 10 08 00 00 00 00
02D0: 70 40 30 00 00 00 00 00 01 92 00 04 00 00 00 02
02E0: 45 44 40 04 00 20 00 00 00 01 00 0B 00 00 00 01
02F0: 1D 00 01 28 00 00 08 08 00 10 00 00 00 00 10 01
One or more memory locations can be deposited as follows:
0200: 00
0200: 8A
eWoz responds with the address and the contents before the deposit. Multiple deposits follow the same syntax:
0201: 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF
0201: B7
0200.020F
0200: 00 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF
Note that eWoz only responds with the pre-deposit contents of the first memory location.
Omitting the start address will continue from the last opened address:
:AA 55 AA 55 AA 55 AA 55 AA 55 AA 55 AA 55 AA 55
0200.021F
0200: AA 55 AA 55 AA 55 AA 55 AA 55 AA 55 AA 55 AA 55
0210: 30 44 30 41 30 30 30 30 37 30 30 30 37 30 31 30
Jump to an address by specifying the address and following it with R:
FD00R
FD00: 78
eWoz responds with the address and its contents, then does a JSR to the memory location provided. The program that is jumped to can RTS to get back to eWoz, provided that the stack has been preserved.
Intel HEX format files can use either DOS/Windows line endings (CR,LF) or UNIX line endings (LF only). Load Intel HEX files as follows:
L
Start Intel Hex code Transfer.
........................
Intel Hex Imported OK.
\
After entering L, press enter. You will be prompted to start the Intel HEX transfer. If the file loads successfully, the message Intel Hex Imported OK. will be printed. If there are checksum errors, Intel Hex Imported with checksum error. will be printed.
The user interrupt vector is at zero page location 0x0040 (low byte) and 0x0041 (high byte). It is initialized to a default IRQ handler to prevent spurious interrupts from crashing the monitor.
This version of eWoz also contains routines to set the console port bitrate using Port A bits PA4 and PA5.
The original Woz monitor was written by Steve Wozniak in 1976. TangentDelta provided the initial port of eWoz and the Makefile to the Glitch Works R65X1Q SBC. Glitch Works, LLC modifications are released under the GNU GPL v3.