Usage Notes; Note On Tas Instruction Usage; Note On Bit Manipulation Instructions - Renesas H8S/2158 User Manual

Section 2 CPU
2.9

Usage Notes

2.9.1

Note on TAS Instruction Usage

The TAS instruction is not generated by the Renesas H8S and H8/300 series C/C++ compilers.
The TAS instruction can be used as a user-defined intrinsic function.
2.9.2

Note on Bit Manipulation Instructions

The BSET, BCLR, BNOT, BST, and BIST instructions read data from the specified address in
byte units, manipulate the data of the target bit, and write data to the same address again in byte
units. Special care is required when using these instructions in cases where a register containing a
write-only bit is used or a bit is directly manipulated for a port, because this may rewrite data of a
bit other than the bit to be manipulated.
Example: The BCLR instruction is executed for DDR in port 4.
P47 and P46 are input pins, with a low-level signal input at P47 and a high-level signal input at
P46. P45 to P40 are output pins and output low-level signals. The following shows an example in
which P40 is set to be an input pin with the BCLR instruction.
Prior to executing BCLR
P47
Input/output Input
Pin state Low
level
DDR 0
DR 1
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P46 P45 P44
Input Output Output
High Low Low
level level level
0 1 1
0 0 0
P43 P42 P41
Output Output Output
Low Low Low
level level level
1 1 1
0 0 0
P40
Output
Low
level
1
0