Bit sequential buffer – NEC PD750008 User Manual
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CHAPTER 5 PERIPHERAL HARDWARE FUNCTIONS
5.7 BIT SEQUENTIAL BUFFER: 16-BIT
The bit sequential buffer (BSB) is special data memory for bit manipulations. In particular, the buffer allows
bit manipulations to be performed very easily by sequentially changing address and bit specifications. So
the buffer is useful in processing long data bit by bit.
This data memory consists of 16 bits, and allows pmem.@L addressing with a bit manipulation instruction.
This addressing uses the L register for indirect bit specification. In this case, only by incrementing or
decrementing the L register in a program loop, the bit to be manipulated can be sequentially shifted for
continued processing.
Figure 5-81. Format of the Bit Sequential Buffer
Remarks 1. With pmem.@L addressing, bit specification is shifted according to the L register.
2. With pmem.@L addressing, BSB can be manipulated at any time regardless of
MBE/MBS specification.
Data can also be manipulated by direct addressing. The buffer can be used for applications such as
continuous 1-bit data input or output operations by combining direct 1-bit, 4-bit, and 8-bit addressing with
pmem.@L addressing. In 8-bit manipulation, the higher eight bits or lower eight bits are manipulated by
specifying BSB0 or BSB2.
3
2
1
0
3
2
1
0
3
2
1
0
3
2
1
0
BSB3
BSB2
BSB1
BSB0
FC3H
FC2H
FC1H
FC0H
L = FH
L = CH
L = BH
L = 8H
L = 7H
L = 4H
L = 3H
L = 0H
DECS L
INCS L
Address
Bit
L register
Symbol