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Chapter 28 Bit Search
4.Register
4. Register
4.1 BSD0: 0 Detection Register / BSD1:1 Detection Register / BSDC: Changing position
Detection Data Register
This is a register for setting the bit search detection data.
• BSD0: Address 03F0
H
(Access: Word)
• BSD1: Address 03F4
H
(Access: Word)
• BSDC: Address 03F8
H
(Access: Word)
(For the attributes, refer to “Meaning of Bit Attribute Symbols (Page No.10)”.)
• Write data used to detect 0, 1 and changing position in each of the registers BSD0, BSD1 and BSDC.
• The result is stored in the detection result register BSRR.
• During 0 detection, the position where “0” is first detected is stored for data written in the order of
MSB(bit31) to LSB(bit0).
• During 1 detection, the position where “1” is first detected is stored for data written in the order of
MSB(bit31) to LSB(bit0).
• During change position detection, the position where a value different from MSB(bit31) is first detected is
stored for data written in the order of bit30 to LSB(bit0).
• The register BSD0 used for 0 detection and the BSRC register used for changing position detection are
write-only. The value during read operation is indefinite.
• Data saved in the bit search can be read if the register BSR1 used to detect 1 is read.
Previous detection result can be restored by re-writing previously read data in the BSR1 used for detecting
1. This applies to the processes for the 0 detection and the changing position detection.This function can be
used to restore a specific state when using a bit search in processing such as interrupt handler.
31 0 bit
BSD0
Indefinite Initial value
W Attribute
31 0 bit
BSD1
Indefinite Initial value
R,W Attribute
31 0 bit
BSDC
Indefinite Initial value
W Attribute