Difference between revisions of "QBUS CPU ODT"

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(Break halts)
(Add extended LSI-11 commands)
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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.
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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]], [[register]]s in the CPU, start the CPU, etc.
  
 
The command set is:
 
The command set is:
  
* '/' - open location
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* '/' - open [[word]]
* '<CR>' - close open location
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* '<CR>' - close open word
* '<LF>' - open next location
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* '<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.)
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==LSI-11s==
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The [[LSI-11 CPUs]], using the [[LSI-11 chip set]], have an extended ODT [[syntax]] with extra commands:
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* '^' - open previous word
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* '@' - indirect; open word at location given by current word
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* '_' - indexed; open word at location given by current word ''plus'' the address of the current word
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* 'M' - maintenance; indicates how the CPU got to ODT
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* '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

See also