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[Prior to executing BSET]
Input/output
Pin state
PCR5
PDR5
[BSET instruction executed]
BSET
#0,
[After executing BSET]
Input/output
Pin state
PCR5
PDR5
[Description on operation]
1. When the BSET instruction is executed, first the CPU reads port 5. Since P57 and P56 are
input pins, the CPU reads the pin states (low-level and high-level input).
P55 to P50 are output pins, so the CPU reads the value in PDR5. In this example PDR5 has a
value of H'80, but the value read by the CPU is H'40.
2. Next, the CPU sets bit 0 of the read data to 1, changing the PDR5 data to H'41.
3. Finally, the CPU writes H'41 to PDR5, completing execution of BSET.
As a result of the BSET instruction, bit 0 in PDR5 becomes 1, and P50 outputs a high-level signal.
However, bits 7 and 6 of PDR5 end up with different values. To prevent this problem, store a copy
of the PDR5 data in a work area in memory. Perform the bit manipulation on the data in the work
area, then write this data to PDR5.
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P57
P56
P55
Input
Input
Output
Low
High
Low
level
level
level
0
0
1
1
0
0
The BSET instruction is executed for port 5.
@PDR5
P57
P56
P55
Input
Input
Output
Low
High
Low
level
level
level
0
0
1
0
1
0
P54
P53
P52
Output
Output
Output
Low
Low
Low
level
level
level
1
1
1
0
0
0
P54
P53
P52
Output
Output
Output
Low
Low
Low
level
level
level
1
1
1
0
0
0
Rev. 1.00, 11/03, page 41 of 376
P51
P50
Output
Output
Low
Low
level
level
1
1
0
0
P51
P50
Output
Output
Low
High
level
level
1
1
0
1
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