LM3S1637 Datasheet, PDF (158/696 Pages) Texas Instruments – ARM and Thumb are registered trademarks and Cortex is a trademark

JTAG Interface
4.1
Block Diagram
Figure 4-1. JTAG Module Block Diagram
TRST
TCK
TMS
TDI
TAP Controller
Instruction Register (IR)
BYPASS Data Register
Boundary Scan Data Register
IDCODE Data Register
ABORT Data Register
DPACC Data Register
APACC Data Register
TDO
Cortex-M3
Debug
Port
4.2 Signal Description
Table 4-1 on page 158 and Table 4-2 on page 159 list the external signals of the JTAG/SWD controller
and describe the function of each. The JTAG/SWD controller signals are alternate functions for
some GPIO signals, however note that the reset state of the pins is for the JTAG/SWD function.
The JTAG/SWD controller signals are under commit protection and require a special process to be
configured as GPIOs, see “Commit Control” on page 291. The column in the table below titled "Pin
Assignment" lists the GPIO pin placement for the JTAG/SWD controller signals. The AFSEL bit in
the GPIO Alternate Function Select (GPIOAFSEL) register (page 305) is set to choose the
JTAG/SWD function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs
(GPIOs)” on page 283.
Table 4-1. JTAG_SWD_SWO Signals (100LQFP)
Pin Name
Pin Number Pin Type Buffer Type^a Description
SWCLK
80
I
TTL
JTAG/SWD CLK.
SWDIO
79
I/O
TTL
JTAG TMS and SWDIO.
SWO
77
O
TTL
JTAG TDO and SWO.
TCK
80
I
TTL
JTAG/SWD CLK.
TDI
78
I
TTL
JTAG TDI.
TDO
77
O
TTL
JTAG TDO and SWO.
TMS
79
I/O
TTL
JTAG TMS and SWDIO.
TRST
89
I
TTL
JTAG TRST.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
158
June 18, 2012
Texas Instruments-Production Data