Detailed Signal Description; Modes Of Operation; External Signal Description; Signal Properties - Motorola ColdFire MCF5281 User Manual

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

Name Direction
JTAG_EN Input
TCLK Input
TMS/BKPT Input
TDI/DSI Input
TRST/DSCLK Input
TDO/DSO Output
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 31-2 summarizes the pin
function selected depending upon JTAG_EN logic state.
Module selected
Pin Function
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
Table 31-1. Signal Properties
Function
JTAG/BDM selector input
JTAG Test clock input
JTAG Test mode select / BDM Breakpoint
JTAG Test data input / BDM Development serial input
JTAG Test reset input / BDM Development serial clock
JTAG Test data output / BDM Development serial output
Table 31-2. Pin Function Selected
JTAG_EN = 0
BDM
—
BKPT
DSI
DSO
DSCLK
Chapter 31. IEEE 1149.1 Test Access Port (JTAG)
Reset State
JTAG_EN = 1 Pin Name
JTAG
TCLK
TMS
TDI
TDO
TRST
Modes of Operation
Pull up
— —
— Active
— Active
— Active
— Active
Hi-Z / 0 —
—
TCLK
BKPT
DSI
DSO
DSCLK
31-3