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Time
8 Cycles
Debug
Clock
Debug
Data
Data Pad
Direction
Cmd Byte
Data Byte 1
Data Byte 2
Output Byte
Input
Input
Output
T0305-01
Start of
Command
Sequence
Pad Is Output, But
Chip Is Not Ready to
Respond
Start to
Change
Direction
End of
Command
Sequence
The Level Is Sampled.
Result = Ready
Chip Is Ready to
Provide Response
The Level Is Sampled.
Result = Not Ready
t
sample_wait
t
dir_change
Debug Commands
Figure 3-4. Typical Command Sequence. Wait for Response
If the debug interface indicates by pulling the data line high that it is not ready to return data, the external
device must issue exactly eight clock pulses before it samples the ready level again. This must be
repeated until the level is low. The wait cycle is equivalent to reading a byte from the debug interface, but
ignoring the result. Note that the pad starts to change direction on the falling edge of the debug clock.
Thus, the pad driver drives against the driver in the programmer until the programmer changes pad
direction. This duration should be minimized in a programmer implementation.
3.3
Debug Commands
The debug commands are shown in
. Some of the debug commands are described in further
detail in the following subsections.
The 3 least-significant bits (the Xs) are don't care values.
Table 3-1. Debug Commands
Additi
Output
Instruction
onal
Bytes
Command
Description
Byte
Input
Bytes
CHIP_ERASE
00010XXX
0
1
Perform flash chip erase (mass erase) and clear lock bits. If any other
command except READ_STATUS is issued, then the use of CHIP_ERASE
is disabled.
Input byte: none
Output byte: Debug status byte. See
.
WR_CONFIG
00011XXX
1
1
Write debug configuration data.
Input byte: See
for details.
Output byte: Debug status byte. See
.
RD_CONFIG
00100XXX
0
1
Read debug configuration data.
Input byte: none.
Output byte: Returns value set by WR_CONFIG command. See
.
56
Debug Interface
SWRU191C
–
April 2009
–
Revised January 2012
Copyright
©
2009
–
2012, Texas Instruments Incorporated