MPC555
/
MPC556
IEEE 1149.1-COMPLIANT INTERFACE (JTAG)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
22-2
Figure 22-2 Test Logic Block Diagram
22.2 JTAG Signal Descriptions
The MPC555 / MPC556 has five dedicated JTAG pins, which are described in
. The TDI and TDO scan ports are used to scan instructions as well as data into
the various scan registers for JTAG operations. The scan operation is controlled by the
test access port (TAP) controller, which in turn is controlled by the TMS input se-
quence.
To enable JTAG on reset for board test, bit 11 (DGPC select JTAG pins) and bit 16
(PRPM peripheral mode enable) of the reset configuration word should be held high
during the rising edge of reset (see
7.5.2 Hard Reset Configuration Word
). These
need to be configurable on the user board to allow JTAG test of a board. To allow nor-
mal operation of the board these bits need to be low in the reset configuration word.
Boundary scan register
Bypass
M
U
X
Instruction apply & decode register
4-bit Instruction register
M
U
X
TDO
TDI
TMS
TCK
TRST
0
1
2
TAP CONTROLLER
3
JCOMP
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..