MC68332
CENTRAL PROCESSING UNIT
USER’S MANUAL
5-19
A double bus fault during initial stack pointer/program counter (SP/PC) fetch sequence
is distinguished by a value of $FFFFFFFF in the current instruction PC. At no other
time will the processor write an odd value into this register.
5.10.2.4 BDM Commands
Commands consist of one 16-bit operation word and can include one or more 16-bit
extension words. Each incoming word is read as it is assembled by the serial interface.
The microcode routine corresponding to a command is executed as soon as the com-
mand is complete. Result operands are loaded into the output shift register to be shift-
ed out as the next command is read. This process is repeated for each command until
the CPU returns to normal operating mode.
mode commands.
Table 5-5 Background Mode Command Summary
Command
Mnemonic
Description
Read D/A Register
RDREG/RAREG Read the selected address or data register and
return the results via the serial interface.
Write D/A Register
WDREG/WAREG The data operand is written to the specified
address or data register.
Read System Register
RSREG
The specified system control register is read. All
registers that can be read in supervisor mode
can be read in background mode.
Write System Register
WSREG
The operand data is written into the specified
system control register.
Read Memory Location
READ
Read the sized data at the memory location
specified by the long-word address. The
source function code register (SFC)
determines the address space accessed.
Write Memory Location
WRITE
Write the operand data to the memory location
specified by the long-word address. The
destination function code (DFC) register
determines the address space accessed.
Dump Memory Block
DUMP
Used in conjunction with the READ command to
dump large blocks of memory. An initial READ
is executed to set up the starting address of
the block and retrieve the first result.
Subsequent operands are retrieved with the
DUMP command.
Fill Memory Block
FILL
Used in conjunction with the WRITE command to
fill large blocks of memory. An initial WRITE is
executed to set up the starting address of the
block and supply the first operand.
Subsequent operands are written with the
FILL command.
Resume Execution
GO
The pipe is flushed and re-filled before resuming
instruction execution at the current PC.
Patch User Code
CALL
Current program counter is stacked at the
location of the current stack pointer.
Instruction execution begins at user patch
code.
Reset Peripherals
RST
Asserts RESET for 512 clock cycles. The CPU is
not reset by this command. Synonymous with
the CPU RESET instruction.
No Operation
NOP
NOP performs no operation and may be used as
a null command.
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
.
..