M54455EVB User’s Manual, Rev. 4
20
Freescale Semiconductor
4.9
BDM and JTAG
The primary debug port on the MCF5445
x
is referred to as the background debug module or BDM. The
standard 26-pin BDM header (J24) is provided on the M54455EVB for attachment of an external BDM
control interface. However, the M54455EVB also features a built-in P&E USB ColdFire Multilink. This
interface is brought out to the I/O back panel to a standard Type-B USB receptacle. Refer to
” for the location of the connector. This allows for run-control debugging with a standard
USB cable (provided in the M54455EVB kit).
The MCF5445
x
also features IEEE 1149.1 Test Access Port (JTAG) test logic that can be used for
boundary-scan testability. The access pins for JTAG are multiplexed over the BDM control signals and are
available on J24.
The JTAG_EN input signal to the MCF5445
x
determines the debug mode: BDM or JTAG. This signal is
controllable by JP903 as shown below.
The TCLK and PSTCLK signals are the only two multiplexed signals that switch input/output state
depending on which debug mode is selected. In BDM mode, the PSTCLK is an output from the MCF5445
x
to the external BDM control interface. In JTAG mode, TCLK is the test clock input. The standard 26-pin
BDM header defines pin 24 as PSTCLK. A common practice is to place TCLK on pin 6 of this header.
JP904 is available to control the routing of the multiplexed TCLK_PSTCLK signal to the 26-pin debug
header (J24) as shown below.
Table 10. Debug Mode Selection
JP903 Setting
Debug Mode
Shunt on 1-2
JTAG
Shunt on 2-3
BDM
Table 11. TCLK/PSTCLK Routing Control
JP904 Setting
TCLK_PSTCLK Routing
Shunt on 1-2
TCLK/PSTCLK on J24[24]
1
1
This setting is required if an external BDM control interface is
used. If the on-board USB Multilink is used, this jumper setting
is ignored.
Shunt on 2-3
TCLK/PSTCLK on J24[6]
2
2
This pin was previously specified by Freescale as Developer
Reserved. External BDM control cables may be able to make
use of this pin for JTAG instructions. There is a 10-k
Ω
pull-down resistor on the TCK_PSTCLK signal when this
setting is selected.