On-line Debugging Tool

For other expansions of "ODT", see ODT.

Octal Debugging Technique, or ODT, was the name of several debugger programs originally developed for DEC hardware. Various operating systems including OS/8, RT-11, RSX-11, and RSTS/E implemented ODT as did the firmware console of all of the LSI-11-family processors including the 11/03, 11/23/24, 11/53, 11/73, and 11/83/84.

The debugger allowed access to memory using octal addresses and data. Within the software systems, the debugger accessed the process's virtual memory. The firmware console implementation accessed physical memory.

Firmware ODT

Access to ODT is obtained either from power up (with appropriate power up mode selected), by the execution of a HALT instruction in kernel mode, or by use of the front panel halt switch or button.

Commands

ODT commands are as follows:

<CR> Close currently open location or register
<LF> Close currently open location or register and open next
P    Proceed, execute next instruction with no imlied reset
<addr>G Load PC with <addr>, reset and commence execution at address
Rn/ or $n/  Open register n
RS/ or $S/  Open PSW

Example

>1000/ xxxxxx 112737<LF> 001002 xxxxxx 101<LF> 001004 xxxxxx 177566<LF> 001006 xxxxxx 137<LF> 001010 xxxxxx 1000<CR> >R7/xxxxxx 1000<CR> >RS/340

This deposits the program

MOVB 'A', 177666  ; Move 'A' into console transmit register
JMP @#1000        ; Jump back to start

sets the PC to the start of the program and sets the PSW to lock out interrupts.

The effect of this will be to write a stream of

See also

• Dynamic Debugging Technique