docs(pps): record live lock diagnosis

2026-07-25 13:32:24 +03:00
parent 971be036a0
commit 0f6b3482c5
2 changed files with 53 additions and 1 deletions
@@ -83,6 +83,27 @@ software polls `STATUS.DIAG_BUSY` before reading the group. The disciplined
 timebase continues in holdover and while the physical output is disabled;
 `CONTROL.ENABLE` gates `pps_out` and validity, not timekeeping.

+This also applies to the single-word `ACTIVE_SEQUENCE` and `PULSE_COUNT`
+registers: they belong to the same frozen diagnostic group. A live debugger
+must halt the CPU briefly, request a new snapshot, wait for status bit 10 to
+clear, and only then read `0x48..0x74`. For example, with OpenOCD's GDB monitor:
+
+```gdb
+monitor halt
+monitor mww 0x1002a078 1
+monitor sleep 10
+x/wx 0x1002a004
+x/wx 0x1002a048
+x/wx 0x1002a05c
+x/wx 0x1002a060
+x/wx 0x1002a074
+monitor resume
+```
+
+Reading `ACTIVE_SEQUENCE` or `PULSE_COUNT` without this request can return the
+previous snapshot, including reset zero, even while the core is accepting
+commits and generating pulses.
+
 Run lint plus both unit-level Questa tests from this directory:

 ```