External Signal Description

Table 31-3. Signal State to the Disable Module

 

JTAG_EN = 0

JTAG_EN = 1

 

 

 

 

 

 

Disabling JTAG

 

 

= 0

 

 

TRST

 

 

TMS = 1

 

 

 

 

 

 

 

Disabling BDM

 

Disable DSCLK

 

 

 

 

 

DSI = 0

 

 

 

 

 

BKPT

= 1

 

 

 

 

 

 

 

NOTE

The JTAG_EN does not support dynamic switching between

JTAG and BDM modes.

31.3.1.2 TCLK — Test Clock Input

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.

31.3.1.3 TMS/BKPT — Test Mode Select / Breakpoint

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.

31.3.1.4 TDI/DSI — Test Data Input / Development Serial Input

The TDI pin is the LSB-first data and instruction input. TDI is sampled on the rising edge of TCLK. The TDI pin has an internal pull-up resistor.

The DSI pin provides data input for the debug module serial communication port.

31.3.1.5 TRST/DSCLK — Test Reset / Development Serial Clock

The TRST pin is an active low asynchronous reset input with an internal pull-up resistor that forces the TAP controller to the test-logic-reset state.

The DSCLK pin clocks the serial communication port to the debug module. Maximum frequency is 1/5 the processor clock speed. At the rising edge of DSCLK, the data input on DSI is sampled and DSO changes state.

31-4

MCF5282 User’s Manual

MOTOROLA

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Image 734
Motorola MCF5282, MCF5281 user manual Tclk Test Clock Input, 31.3.1.3 TMS/BKPT Test Mode Select / Breakpoint