Modes of Operation

31.2 Modes of Operation

The JTAG_EN pin can select between the following modes of operation:

JTAG mode

BDM - background debug mode (For more information, refer to Section 29.5, “Background Debug Mode (BDM)).”

31.3 External Signal Description

The JTAG module has five input and one output external signals, as described in Table 31-1.

 

31.3.1

Detailed Signal Description

 

 

 

 

 

 

 

 

Table 31-1. Signal Properties

 

 

 

 

 

 

 

 

 

Name

Direction

Function

Reset State

Pull up

 

 

 

 

 

 

 

JTAG_EN

Input

JTAG/BDM selector input

 

 

 

 

 

 

 

TCLK

Input

JTAG Test clock input

Active

 

 

 

 

 

 

 

 

 

 

 

 

 

Input

JTAG Test mode select / BDM Breakpoint

Active

 

TMS/BKPT

 

 

 

 

 

 

 

 

TDI/DSI

Input

JTAG Test data input / BDM Development serial input

Active

 

 

 

 

 

 

 

 

 

 

 

Input

JTAG Test reset input / BDM Development serial clock

Active

 

TRST/DSCLK

 

 

 

 

 

 

 

TDO/DSO

Output

JTAG Test data output / BDM Development serial output

Hi-Z / 0

 

 

 

 

 

 

 

 

 

31.3.1.1 JTAG_EN — JTAG Enable

The JTAG_EN pin selects between Debug module and JTAG. If JTAG_EN is low, the Debug module is selected; if it is high, the JTAG is selected. Table 31-2summarizes the pin function selected depending upon JTAG_EN logic state.

Table 31-2. Pin Function Selected

 

JTAG_EN = 0

JTAG_EN = 1

Pin Name

 

 

 

 

 

Module selected

 

BDM

JTAG

 

 

 

 

 

Pin Function

 

TCLK

TCLK

 

 

BKPT

 

TMS

BKPT

 

 

DSI

TDI

DSI

 

 

DSO

TDO

DSO

 

DSCLK

TRST

DSCLK

 

 

 

 

 

 

When one module is selected, the inputs into the other module are disabled or forced to a known logic level as shown in Table 31-3,in order to disable the corresponding module.

MOTOROLA

Chapter 31. IEEE 1149.1 Test Access Port (JTAG)

31-3

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Image 733
Motorola MCF5281 External Signal Description, Detailed Signal Description, Jtagen Jtag Enable, Pin Function Selected