User’s Manual U14826EJ5V0UD
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CHAPTER 12 BIT SEQUENTIAL BUFFER
12.1 Bit Sequential Buffer Functions
The
µ
PD789860, 789861 Subseries have an on-chip bit sequential buffer of 8 bits + 8 bits = 16 bits.
The functions of the bit sequential buffer are shown below.
• If the value of the bit sequential buffer 10 data register (BSFRL10, BSFRH10) is shifted 1 bit to the lower side,
the LSB can be output to the port at the same time.
• It is possible to write to BSFRL10 and BSFRH10 using an 8-bit or 16-bit memory manipulation instruction
(reading is not possible).
• Overwriting is enabled during a shift operation on the higher 8 bits (BSFRH10) only (the period in which shift
clock is low level).
12.2 Bit Sequential Buffer Configuration
The bit sequential buffer includes the following hardware.
Table 12-1. Configuration of Bit Sequential Buffer
Item Configuration
Data register
Bit sequential buffer: 8 bits + 8 bits = 16 bits
Control register
Bit sequential buffer output control register 10 (BSFC10)
Port mode register 2 (PM2)
Port 2 (P2)
Figure 12-1. Block Diagram of Bit Sequential Buffer
Bit sequential buffer output
control register 10 (BSFC10)
Internal bus
Timer 40 match
interrupt request signal
BSFRH10
BSFRL10
Internal bus
BSFE10
BSFO/P20/
TMO
P20
output latch
PM20