System Development and Debugging
MPC885 PowerQUICC Family Reference Manual, Rev. 2
53-20
Freescale Semiconductor
•
Debug mode can be entered immediately out of reset, allowing the user to debug a system without
using ROM.
•
The debug enable register (DER) can be used to selectively enable events that cause the machine
to enter debug mode.
•
The interrupt cause register (ICR) indicates why debug mode is entered.
•
After entry into debug mode, program execution continues from the where debug mode was
entered.
•
All instructions are fetched from the development port, while load/store accesses are performed on
the real system memory in debug.
•
A simple method is provided for memory dump and load via the data register of the development
port that is accessed with mtspr and mfspr.
•
The processor enters privileged state (MSR[PR] = 0) in debug mode, allowing execution of any
instruction and access to any memory location.
•
An OR signal of all interrupt cause register (ICR) bits enables the development port to
detect pending events while already in debug mode. For example, the development port can
detect a debug mode access to a nonexisting memory space.
•
Caches and MMUs are frozen in debug mode. All accesses made during debug mode will
be to the memory. Cache contents can only be accessed via SPRs.
53.3.1.1
Debug Mode Enable vs. Debug Mode Disable
For protection purposes, there are two working modes, debug mode enable and debug mode disable, which
are selected once at reset. Debug mode is enabled by asserting DSCK during reset. The state of this pin is
sampled three clocks before the negation of SRESET. If DSCK is sampled negated, debug mode is
disabled until a subsequent reset when DSCK is asserted. When debug mode is disabled, the internal
watchpoint/breakpoint hardware remains operational and can be used for debugging by a software monitor
program.
Figure 53-7
is a timing diagram for the enabling debug mode.
Figure 53-7. Debug Mode Reset Configuration Timing Diagram
Note that because SRESET negation time depends on an external pull-up resistor, any reference to
SRESET negation time in this chapter refers to the time the MPC885 releases SRESET. If SRESET rise
DSCK
CLKOUT
SRESET
DSCK asserts high while SRESET asserted to enable debug mode operation.
0
1
2
3
4
5
8
9
10
11
12
13
14
15
16
17
DSCK asserts high after SRESET negation to enter debug mode immediately (without fetching reset vector).
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...