h8s-2635 Renesas Electronics Corporation., h8s-2635 Datasheet - Page 137

• Manufacturer Part Number: h8s-2635
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

2.10
2.10.1
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 Family 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.
2.10.2
With STM and LDM instructions, register ER7 cannot be used as a register that can be saved
(STM) or restored (LDM) since it is the stack pointer.
The number of registers that can be saved (STM) or restored (LDM) by a single instruction is two,
three, or four. The registers that can be used in these cases are as follows.
Two registers: ER0–ER1, ER2–ER3, ER4–ER5
Three registers: ER0–ER2, ER4–ER6
Four registers: ER0–ER3
The Renesas Technology H8S Family and H8/300 Series C/C++ compilers do not generate
STM/LDM instructions that include ER7.
2.10.3
The BSET, BCLR, BNOT, BST, and BIST instructions read data in a unit of byte, then, after bit
manipulation, they write data in a unit of byte. Therefore, caution must be exercised when
executing any of these instructions for registers and ports that include write-only bits.
The BCLR instruction can be used to clear the flag of an internal I/O register to 0. In that case, if it
is clearly known that the pertinent flag is set to 1 in an interrupt processing routine or other
processing, there is no need to read the flag in advance.
Usage Note
TAS Instruction
STM/LDM Instructions
Caution to Observe when Using Bit Manipulation Instructions
Rev. 6.00 Feb 22, 2005 page 77 of 1484
REJ09B0103-0600
Section 2 CPU