HD404849 Datasheet, PDF (80/125 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

SO
SCK
SI
Idle
controller
I/O
controller
Octal
counter (OC)
Clock
1/2
1/2
HD404849 Series
Serial interrupt
request flag
(IFS)
Serial data
register (SR)
Transfer
control
signal
System
clock
ø_PER
Selector
3
Serial mode
register A
(SMRA)
Prescaler S (PSS)
Serial mode
register B
(SMRB)
Figure 66 Block Diagram of Serial Interface
Serial Interface Operation
Selecting and Changing the Operating Mode: Table 28 lists the serial interface’s operating modes. To
select an operating mode, use one of these combinations of port mode register A (PMRA: $004) and serial
mode register A (SMRA: $005) settings; to change the operating mode, always initialize the serial interface
internally by writing data to serial mode register A. Note that the serial interface is initialized by writing
data to serial mode register A. Refer to the following Serial Mode Register A section for details.
Table 28 Serial Interface Operating Modes
SMRA PMRA
Bit 3 Bit 1 Bit 0
1
0
0
1
1
0
1
Operating Mode
Clock continuous output mode
Transmit mode
Receive mode
Transmit/receive mode
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