Typical Command Sequence-No Extra Wait For Response - Texas Instruments CC253x User Manual

Debug Communication
A debug command sequence always starts with the host transmitting a command through the serial
interface. This command encodes the number of bytes containing further parameters to follow, and
whether a response is required. Based on this command, the debug module controls the direction of the
debug data pad. A typical command sequence is shown in
simplified for the clarity of the figure, not showing each individual bit change. The direction is not explicitly
indicated to the outside world, but must be derived by the host from the command protocol.
Time
Debug
Clock
Debug
Cmd Byte
Data
Data Pad
Input
Direction
Figure 3-3. Typical Command Sequence—No Extra Wait for Response
For commands that require a response, there must be a small idle period between the command and the
response to allow the pad to change direction. After the minimum waiting time (t
indicates whether it is ready to deliver the response data by pulling the data pad low. The external
debugger, which is sampling the data pad, detects this and begins to clock out the response data. If the
data pad is high after the waiting time, it is an indication to the debugger that the chip is not ready yet.
Figure 3-4 shows how the wait works.
52
Debug Interface
Start of
Command
Sequence
Start to
Change
Direction
Data Byte 1 Data Byte 2
Copyright © 2009–2014, Texas Instruments Incorporated
Figure 3-3. Note that the debug-data signal is
Pad is
Output
Output
t
dir_change
SWRU191F – April 2009 – Revised April 2014
www.ti.com
End of
Command
Sequence
Output Byte
Input
The Level is
Sampled by the
External Device
(Asynchronously)
) of 83 ns, the chip
dir_change
Submit Documentation Feedback
T0304-01