LM3S6938 Luminary Micro, Inc, LM3S6938 Datasheet - Page 51

• Manufacturer Part Number: LM3S6938
• Description: Lm3s6938 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

5.2.3
5.2.4
July 25, 2008
Figure 5-2. Test Access Port State Machine
Shift Registers
The Shift Registers consist of a serial shift register chain and a parallel load register. The serial shift
register chain samples specific information during the TAP controller’s CAPTURE states and allows
this information to be shifted out of TDO during the TAP controller’s SHIFT states. While the sampled
data is being shifted out of the chain on TDO, new data is being shifted into the serial shift register
on TDI. This new data is stored in the parallel load register during the TAP controller’s UPDATE
states. Each of the shift registers is discussed in detail in “Register Descriptions” on page 54.
Operational Considerations
There are certain operational considerations when using the JTAG module. Because the JTAG pins
can be programmed to be GPIOs, board configuration and reset conditions on these pins must be
considered. In addition, because the JTAG module has integrated ARM Serial Wire Debug, the
method for switching between these two operational modes is described below.
1
0
Test Logic Reset
Run Test Idle
0
1
1
0
Preliminary
Select DR Scan
Capture DR
Update DR
Pause DR
Exit 1 DR
Exit 2 DR
Shift DR
1
0
0
1
0
1
1
0
1
0
1
0
1
0
LM3S6938 Microcontroller
Select IR Scan
Capture IR
Update IR
Pause IR
Exit 1 IR
Exit 2 IR
Shift IR
1
0
0
1
0
1
1
0
1
0
1
0
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