QBUS CPU ODT: Difference between revisions
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'''ODT (Octal Debugging Technique)''' on [[QBUS]] [[PDP-11]]s is effectively their [[front panel]]. These [[Central Processing Unit|CPUs]] do not have a front panel to control them; instead, as a cost-reduction measure, when the CPU is [[halt]]ed, specialized [[microcode]] uses the main [[asynchronous serial line|serial line]] as a operating console. There are commands to read and write [[main memory]], start the CPU, etc. | '''ODT (Octal Debugging Technique)''' on [[QBUS]] [[PDP-11]]s is effectively their [[front panel]]. These [[Central Processing Unit|CPUs]] do not have a front panel to control them; instead, as a cost-reduction measure, when the CPU is [[halt]]ed, specialized [[microcode]] uses the main [[asynchronous serial line|serial line]] as a operating console. There are commands to read and write [[main memory]], [[register]]s in the CPU, start the CPU, etc. | ||
The command set is: | The command set is: | ||
* '/' - open | * '/' - open [[word]] | ||
* '<CR>' - close open | * '<CR>' - close open word | ||
* '<LF>' - open next | * '<LF>' - open next word | ||
* 'G' - start CPU | * 'G' - start CPU | ||
* 'P' - proceed CPU after halt | * 'P' - proceed CPU after halt | ||
The main serial interface is normally configured so that when the CPU is running, sending a [[asynchronous serial line|break]] on the console serial line halts the CPU. (Depending on which interface card is used, some can be set to [[bootstrap]] the machine instead.) | The main serial interface is normally configured so that when the CPU is running, sending a [[asynchronous serial line|break]] on the console serial line halts the CPU. (Depending on which interface card is used, some can be set to [[bootstrap]] the machine instead.) | ||
==LSI-11s== | |||
The [[LSI-11 CPUs]], using the [[LSI-11 chip set]], have an extended ODT [[syntax]] with extra commands: | |||
* '^' - open previous word | |||
* '@' - indirect; open word at location given by current word | |||
* '_' - indexed; open word at location given by current word ''plus'' the address of the current word | |||
* 'M' - maintenance; indicates how the CPU got to ODT | |||
* 'L' - start microcode [[PDP-11 Bootstrap Loader]] | |||
==See also== | ==See also== | ||
Revision as of 18:41, 19 August 2019
ODT (Octal Debugging Technique) on QBUS PDP-11s is effectively their front panel. These CPUs do not have a front panel to control them; instead, as a cost-reduction measure, when the CPU is halted, specialized microcode uses the main serial line as a operating console. There are commands to read and write main memory, registers in the CPU, start the CPU, etc.
The command set is:
- '/' - open word
- '<CR>' - close open word
- '<LF>' - open next word
- 'G' - start CPU
- 'P' - proceed CPU after halt
The main serial interface is normally configured so that when the CPU is running, sending a break on the console serial line halts the CPU. (Depending on which interface card is used, some can be set to bootstrap the machine instead.)
LSI-11s
The LSI-11 CPUs, using the LSI-11 chip set, have an extended ODT syntax with extra commands:
- '^' - open previous word
- '@' - indirect; open word at location given by current word
- '_' - indexed; open word at location given by current word plus the address of the current word
- 'M' - maintenance; indicates how the CPU got to ODT
- 'L' - start microcode PDP-11 Bootstrap Loader
