Difference between revisions of "QBUS CPU ODT"
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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 19:41, 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
