HD6473847RHV Datasheet, PDF (97/546 Pages) Renesas Technology Corp – Renesas 8-Bit Single-Chip Microcomputer H8 Family / H8/300L Super Low Power Series

Section 2 CPU
Byte size instructions should therefore be used when transferring data to or from I/O registers
other than the on-chip ROM and RAM areas.
2.9.3 EEPMOV Instruction
EEPMOV is a block-transfer instruction and transfers the byte size of data indicated by R4L,
which starts from the address indicated by R5, to the address indicated by R6. Set R4L and R6 so
that the end address of the destination address (value of R6 + R4L) does not exceed H'FFFF (the
value of R6 must not change from H'FFFF to H'0000 during execution).
2.9.4 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 two registers are
assigned to the same address or when a bit is directly manipulated for a port, because this may
rewrite data of a bit other than the bit to be manipulated.
Bit Manipulation in Two Registers Assigned to Same Address:
Example 1: Timer load register and timer counter
Figure 2.17 shows an example of a timer in which two timer registers are assigned to the same
address. When a bit manipulation instruction accesses the timer load register and timer counter of
a reloadable timer, since these two registers share the same address, the following operations takes
place.
1. Data is read in byte units.
2. The CPU sets or resets the bit to be manipulated with the bit manipulation instruction.
3. The written data is written again in byte units to the timer load register.
The timer is counting, so the value read is not necessarily the same as the value in the timer load
register. As a result, bits other than the intended bit in the timer counter may be modified and the
modified value may be written to the timer load register.
Rev. 7.00 Mar. 08, 2010 Page 65 of 510
REJ09B0024-0700