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IEEE 1149.1 Test Access Port (JTAG)
Freescale Semiconductor
35-3
When one module is selected, the inputs into the other module are disabled or forced to a known logic
level, as shown in
, to disable the corresponding module.
NOTE
The JTAG_EN does not support dynamic switching between JTAG and
BDM modes.
35.2.2
Test Clock Input (TCLK)
The TCLK pin is a dedicated JTAG clock input to synchronize the test logic. Pulses on TCLK shift data
and instructions into the TDI pin on the rising edge and out of the TDO pin on the falling edge. TCLK is
independent of the processor clock. The TCLK pin has an internal pull-up resistor, and holding TCLK high
or low for an indefinite period does not cause JTAG test logic to lose state information.
35.2.3
Test Mode Select/Breakpoint (TMS/BKPT)
The TMS pin is the test mode select input that sequences the TAP state machine. TMS is sampled on the
rising edge of TCLK. The TMS pin has an internal pull-up resistor.
The BKPT pin is used to request an external breakpoint. Assertion of BKPT puts the processor into a halted
state after the current instruction completes.
35.2.4
Test Data Input/Development Serial Input (TDI/DSI)
The TDI pin receives serial test and data, which is sampled on the rising edge of TCLK. Register values
are shifted in least significant bit (lsb) first. The TDI pin has an internal pull-up resistor.
The DSI pin provides data input for the debug module serial communication port.
Table 35-2. Pin Function Selected
JTAG_EN = 0
JTAG_EN = 1
Pin Name
Module selected
BDM
JTAG
—
Pin Function
—
BKPT
DSI
DSO
DSCLK
TCLK
TMS
TDI
TDO
TRST
TCLK
BKPT
DSI
DSO
DSCLK
Table 35-3. Signal State to the Disable Module
JTAG_EN = 0
JTAG_EN = 1
Disabling JTAG
TRST = 0
TMS = 1
—
Disabling BDM
—
Disable DSCLK
DSI = 0
BKPT = 1
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...