HD6433682 ETC, HD6433682 Datasheet - Page 75

• Manufacturer Part Number: HD6433682
• Description: Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series
• Manufacturer: ETC

Input/output
Pin state
PCR5
PDR5
Input/output
Pin state
PCR5
PDR5
1. When the BCLR instruction is executed, first the CPU reads PCR5. Since PCR5 is a write-only
2. Next, the CPU clears bit 0 in the read data to 0, changing the data to H'FE.
3. Finally, H'FE is written to PCR5 and BCLR instruction execution ends.
BCLR
Prior to executing BCLR instruction
BCLR instruction executed
After executing BCLR instruction
Description on operation
register, the CPU reads a value of H'FF, even though the PCR5 value is actually H'3F.
As a result of this operation, bit 0 in PCR5 becomes 0, making P50 an input port. However,
bits 7 and 6 in PCR5 change to 1, so that P57 and P56 change from input pins to output pins.
To prevent this problem, store a copy of the PDR5 data in a work area in memory and
manipulate data of the bit in the work area, then write this data to PDR5.
#0,
P57
Input
Low
level
0
1
P57
Output
Low
level
1
1
@PCR5
P56
Input
High
level
0
0
P56
Output
High
level
1
0
P55
Output
Low
level
1
0
P55
Output
Low
level
1
0
The BCLR instruction is executed for PCR5.
P54
Output
Low
level
1
0
P54
Output
Low
level
1
0
P53
Output
Low
level
1
0
P53
Output
Low
level
1
0
Rev. 3.00, 05/03, page 45 of 472
P52
Output
Low
level
1
0
P52
Output
Low
level
1
0
1
0
0
P51
Output
Low
level
P51
Output
Low
level
1
P50
Output
Low
level
1
0
P50
Input
High
level
0
0