Program Trace Message Fields - STMicroelectronics SPC572L series Reference Manual

RM0400
(1–32 bits)
Relative Address
Max length = 51 bits; Min length = 13 bits
66.12.2.3 Direct branch messages (traditional)
Direct branches (conditional or unconditional) are all taken branches whose destination is
fixed in the instruction opcode. Direct branch information is messaged out in the following
format:
Max length = 18 bits; Min length = 11 bits
Note: When DC1
branch, not-taken indirect branch, or predicated instruction will be recorded in the history
buffer.
66.12.3

Program Trace Message Fields

The following subsections describe specific fields used for Program Trace messages.
66.12.3.1 Sequential Instruction Count Field (ICNT)
Most of the program trace messages include an instruction count field. For traditional
Branch messages, ICNT represents the number of sequential instructions including non-
taken branches since the last Direct/Indirect Branch messages. Branch instructions that
trigger message generation are included in the ICNT.
For Branch History messages, ICNT represents the number of instructions executed since
the last taken/non-taken direct branch, predicate instruction, last taken/not-taken indirect
branch, or exception. Branch instructions that trigger message generation are included in
the ICNT. Instructions that generate history bits are not included in the ICNT.
The sequential instruction counter overflows after its value reaches 255 and is reset to 0. In
addition, the next BTM Message (corresponding to the 256th or later instruction) will be
converted to a w/sync type message.
The instruction counter is reset every time the instruction count is transmitted in a message
or whenever there is a branch/predicate history event, as well as on exiting from debug
mode.
66.12.3.2 Branch/Predicate Instruction History (HIST)
If DC1
PTM
(HIST) field in these messages provides a history of branch execution used for
reconstructing the program flow. The branch/predicate history buffer stores information
about branch and predicate instruction execution. The buffer is implemented as a left-
shifting register. The buffer is preloaded with a one (1), which acts as a stop bit (the most
Figure 1164. Indirect branch message format
(1–8 bits)
Sequence Count
Figure 1165. Direct branch message format
(1–8 bits)
Sequence Count
is set, Direct Branch Messages will not be transmitted. Instead, each direct
PTM
is set, BTM messaging will use the Branch History format. The branch history
DocID027809 Rev 4
(1 bit)
(4 bits)
Source
(0)
Proc.
(4 bits) (6 bits)
Src. Proc. TCODE (000011)
e200z215An3 Nexus 3 Module
(6 bits)
TCODE (000100)
1953/2058
1982