H8S2258 Datasheet, PDF (184/1071 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8S Family/H8S/2200 Series

Section 2 CPU
2.9 Usage Notes
2.9.1 TAS Instruction
Only register ER0, ER1, ER4, or ER5 should be used when using the TAS instruction. The TAS
instruction is not generated by the Renesas Technology H8S and H8/300 Series C/C++ compilers.
If the TAS instruction is used as a user-defined intrinsic function, ensure that only register ER0,
ER1, ER4, or ER5 is used.
2.9.2 STM/LDM Instruction
With the STM or LDM instruction, the ER7 register is used as the stack pointer, and thus cannot
be used as a register that allows save (STM) or restore (LDM) operation.
With a single STM or LDM instruction, two to four registers can be saved or restored. The
available registers are as follows:
For two registers: ER0 and ER1, ER2 and ER3, or ER4 and ER5
For three registers: ER0 to ER2, or ER4 to ER6
For four registers: ER0 to ER3
For the Renesas Technology H8S or H8/300 Series C/C++ Compiler, the STM/LDM instruction
including ER7 is not created.
2.9.3 Bit Manipulation Instructions
When a register that includes write-only bits is manipulated by a bit manipulation instruction,
there are cases where the bits manipulated are not manipulated correctly or bits unrelated to the
bits manipulated are changed.
When a register containing write-only bits is read, the value read is either a fixed value or an
undefined value. This means that the bit manipulation instructions that use the value of bits read in
their operation (BNOT, BTST, BAND, BIAND, BOR, BIOR, BXOR, BIXOR, BLD, and BILD)
will not perform correct bit operations.
Also, bit manipulation instructions that perform a write operation on the data read after the
calculation (BSET, BCLR, BNOT, BST, and BIST) may change bits unrelated to the bits
manipulated. Thus extreme care is required when performing bit manipulation instructions on
registers that include write-only bits.
Rev. 5.00 Aug 08, 2006 page 98 of 982
REJ09B0054-0500