QBUS CPU ODT - Revision history

Jnc: /* Further reading */ +Micro ODT Differences - LSI-11 vs. LSI-11/23

2024-07-25T13:25:26Z

‎Further reading: +Micro ODT Differences - LSI-11 vs. LSI-11/23

Jnc: better section title

2021-10-22T03:59:24Z

better section title

Jnc: Need for working memory at 0 on LSI-11s

2021-10-22T00:52:43Z

Need for working memory at 0 on LSI-11s

Jnc: Add extended LSI-11 commands

2019-08-19T18:41:30Z

Add extended LSI-11 commands

Jnc: Break halts

2019-08-19T17:38:25Z

Break halts

Jnc: Pretty complete

2019-08-19T16:08:18Z

Pretty complete

New page

'''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.

The command set is:

* '/' - open location
* '<CR>' - close open location
* '<LF>' - open next location
* 'G' - start CPU
* 'P' - proceed CPU after halt

==See also==

* [[LSI-11 CPUs]]
* [[KDF11 CPUs]]
* [[KDJ11 CPUs]]

[[Category: PDP-11s]]

@@ Line 21: / Line 21: @@
 * 'L' - start microcode [[PDP-11 Bootstrap Loader]]
-==Limitations==
+===Limitation on LSI-11s===
 Note that ODT will not function correctly in the LSI-11s unless there is memory on the QBUS (at location 0). Without that, the CPU will sit in a tight [[loop]], trying to read location 0, and ODT will never start. The reason for this restriction is unknown: the [[KDF11 CPUs]] and [[KDJ11 CPUs]], which also use ODT, do not have this limitation; e.g. a system consisting only of a [[KDF11-A CPU]] and a serial console will run ODT, which will operate as expected.

@@ Line 9: / Line 9: @@
 * '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 (using the BHALT line of the standard [[QBUS]]). Depending on which interface card is used, some can be set to [[bootstrap]] the machine instead.
 ==LSI-11s==
@@ Line 20: / Line 20: @@
 * 'M' - maintenance; indicates how the CPU got to ODT
 * 'L' - start microcode [[PDP-11 Bootstrap Loader]]
 ==See also==

@@ Line 30: / Line 30: @@
 * [[KDF11 CPUs]]
 * [[KDJ11 CPUs]]
 [[Category: PDP-11s]]

@@ Line 1: / Line 1: @@
-'''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:
-* '/' - open location
+* '/' - open [[word]]
-* '<CR>' - close open location
+* '<CR>' - close open word
-* '<LF>' - open next location
+* '<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 [[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.)
 ==See also==