Freescale Semiconductor, Inc.
Register Field:
The system control register is specified by the register field (see Table 5-24). The FAR
is a read-only register—any write to it is ignored.
5.6.2.8.8 Read Memory Location (READ). Read the sized data at the memory location
specified by the long-word address. Only absolute addressing is supported. The SFC
register determines the address space accessed. Valid data sizes include byte, word, or
long word.
Command Format:
15
0
14
0
13
0
12
1
11
1
10
0
9
0
8
1
7
6
5
0
4
0
3
0
2
0
1
0
0
0
OP SIZE
Command Sequence:
READ
MEMORY
LOCATION
READ (B/W)
MS ADDR
"NOT READY"
LS ADDR
"NOT READY"
XXX
"NOT READY"
???
XXX
"ILLEGAL"
NEXT CMD
"NOT READY"
NEXT CMD
RESULT
XXX
NEXT CMD
BERR/AERR
"NOT READY"
READ
MEMORY
LOCATION
READ (LONG)
???
MS ADDR
"NOT READY"
LS ADDR
"NOT READY"
XXX
"NOT READY"
XXX
"ILLEGAL"
NEXT CMD
"NOT READY"
XXX
MS RESULT
NEXT CMD
LS RESULT
XXX
NEXT CMD
BERR/AERR
"NOT READY"
Operand Data:
The single operand is the long-word address of the requested memory location.
Result Data:
The requested data is returned as either a word or long word. Byte data is returned in
the least significant byte of a word result, with the upper byte cleared. Word results
return 16 bits of significant data; long-word results return 32 bits.
A successful read operation returns data bit 16 cleared. If a bus or address error is
encountered, the returned data is $10001.
5.6.2.8.9 Write Memory Location (WRITE). Write the operand data to the memory
location specified by the long-word address. The DFC register determines the address
MOTOROLA
MC68340 USER’S MANUAL
5- 79
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