MPC555
/
MPC556
DEVELOPMENT SUPPORT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
21-38
21.5.6.5 Development Port Serial Communications — Trap Enable Mode
When in not in debug mode the development port starts communications by setting
DSDO (the MSB of the 35-bit development port shift register) low to indicate that all
activity related to the previous transmission are complete and that a new transmission
may begin. The start of a serial transmission from an external development tool to the
development port is signaled by a start bit. A mode bit in the transmission defines the
transmission as either a trap enable mode transmission or a debug mode transmis-
sion. If the mode bit is set the transmission will only be 10 bits long and only seven
data bits will be shifted into the shift register. These seven bits will be latched into the
TECR. A control bit determines whether the data is latched into the trap enable and
VSYNC bits of the TECR or into the breakpoints bits of the TECR.
21.5.6.6 Serial Data into Development Port — Trap Enable Mode
The development port shift register is 35 bits wide but trap enable mode transmissions
only use the start/ready bit, a mode/status bit, a control/status bit, and the seven least
significant data bits. The encoding of data shifted into the development port shift reg-
ister (through the DSDI pin) is shown in
below:
The watchpoint trap enables and VSYNC functions are described in section
Watchpoints and Breakpoints Support
and section
Table 21-10 Trap Enable Data Shifted into Development Port Shift Register
Start
Mode
Con-
trol
1st
2nd
3rd
4th
1st
2nd
VSYNC
Function
- - - - - - Instruction- - - - - -
- - Data- -
Watchpoint Trap Enables
1
1
0
0 = disabled; 1 = enabled
Transfer Data to
Trap Enable
Control Register
Table 21-11 Debug Port Command Shifted Into Development Port Shift Register
Start
Mode
Con-
trol
Extended
Opcode
Major Opcode
Function
1
1
1
x
x
00000
NOP
00001
Hard Reset request
00010
Soft Reset request
0
x
00011
Reserved
1
0
00011
End Download procedure
1
1
00011
Start Download procedure
x
x
00100... 11110 Reserved
x
0
11111
Negate Maskable breakpoint.
x
1
11111
Assert Maskable breakpoint.
0
x
11111
Negate Non Maskable breakpoint.
1
x
11111
Assert Non Maskable breakpoint.
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
.
..