Debug support (DBG)
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The debugger must then program the Trace Mode by writing the PROTOCOL[1:0] bits in the
SPP_R (Selected Pin Protocol) register of the TPIU.
•
PROTOCOL=00: Trace Port Mode (synchronous)
•
PROTOCOL=01 or 10: Serial Wire (Manchester or NRZ) Mode (asynchronous mode).
Default state is 01
It then also configures the TRACE port size by writing the bits [3:0] in the CPSPS_R
(Current Sync Port Size Register) of the TPIU:
•
0x1 for 1 pin (default state)
•
0x2 for 2 pins
•
0x8 for 4 pins
33.15.3 TPUI
formatter
The formatter protocol outputs data in 16-byte frames:
•
seven bytes of data
•
eight bytes of mixed-use bytes consisting of:
–
1 bit (LSB) to indicate it is a DATA byte (‘0) or an ID byte (‘1).
–
7 bits (MSB) which can be data or change of source ID trace.
•
one byte of auxiliary bits where each bit corresponds to one of the eight mixed-use
bytes:
–
if the corresponding byte was a data, this bit gives bit0 of the data.
–
if the corresponding byte was an ID change, this bit indicates when that ID change
takes effect.
Note:
Refer to the ARM
®
CoreSight Architecture Specification v1.0 (ARM
®
IHI 0029B) for further
information
33.15.4 TPUI frame synchronization packets
The TPUI can generate two types of synchronization packets:
•
The Frame Synchronization packet (or Full Word Synchronization packet)
It consists of the word: 0x7F_FF_FF_FF (LSB emitted first). This sequence can not
occur at any other time provided that the ID source code 0x7F has not been used.
It is output periodically
between
frames.
In continuous mode, the TPA must discard all these frames once a synchronization
frame has been found.
•
The Half-Word Synchronization packet
It consists of the half word: 0x7F_FF (LSB emitted first).
It is output periodically
between or within
frames.
These packets are only generated in continuous mode and enable the TPA to detect
that the TRACE port is in IDLE mode (no TRACE to be captured). When detected by
the TPA, it must be discarded.