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350 VM/HSC 6.0 System Programmer’s Guide
1st ed., 6/30/04 - 312579601
Master Trace Table Header
A data area, called the Master Trace Table Header (MTTH) is a 32-byte header which
describes the actual trace table. The address of the MTTH is in the 4-byte area at absolute
address x’54’ (label TRCTAB in structure NUCON). The MTTH actually resides in the
CVT at offset x’238’ (label CVTMTTH).
The format of the MTTH is:
*-------------------------------------------*
x’00’ | MTTCURR | MTTFIRST | MTTLAST | reserved |
*-------------------------------------------*
x’10’ | MTTWRAP | MTTQCNT | MTTQLIM | ‘MTT’ |
*-------------------------------------------*
Trace Table Entries
Each trace table entry (TTE) is 32 bytes long. The default trace table size is 8k bytes (256
entries). All SCP events are recorded, regardless of the state of the external trace (SCP
‘TRACE command). ‘‘USR’’ events (GTRACE) events are never recorded in the SCP
internal trace table. Instead, USR events generated by the HSC are recorded in the HSC
internal trace table.
The TTE contains common information about every event, and some data specific to each
event type.
* STANDARD TRACE TABLE ENTRY (TTE)
Offset *------------------------------------------------*
x’00’ | PSW at the time of the event |
*------------------------------------------------*
x’08’ | event | | event | TTEWORD1 ( 4 bytes of |
| type | flag | code | event-dependent data) |
*------------------------------------------------*
x’10’ | TTEWORD2 ( 4 bytes of | TTEWORD3 ( 4 bytes of |
| event-dependent data)| event-dependent data) |
*------------------------------------------------*
x’18’ | TBLOK address | TOD (bytes 3-6) |
| of current task | at time of event |
*------------------------------------------------*
MTTCURR the address of the current TTE (actually the last entry made)
MTTFIRST the address of first TTE MTTLAST the address of (byte after) last entry
MTTLAST the address of (byte after) last entry
MTTWRAP is the TOD (bytes 3-6) of last wrap (or first entry)
MTTQCNT is the number of events queued since POSTING (since TRACE task was
POSTed)
MTTQLIM is the number of events to queue before POSTING
MTTEYE is the eye catcher: c’MTT ‘