7220 Datasheet, PDF (67/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

FUNCTIONAL DESCRIPTION
2.7 Serial I/O
2.7 Serial I/O
The M37221M6-XXXSP/FP has on-chip clock synchronous serial I/O which can receive and transmit 8-bit
data serially.
Because pin SOUT also can be used as the serial I/O data input pin, it can transmit and receive with only
one signal line.
2.7.1 Structure of serial I/O
Serial I/O consists of
q Serial I/O register
q Serial I/O mode register
q Serial I/O counter
q Clock source generating counter
The serial I/O register is the register which 8-bit transfer data is written into. Each function of serial I/O
can be controlled by setting appropriate values to the serial I/O mode register.
Serial I/O transfers data to and from the internal CPU via the data bus, and it transfers data to and from
external devices via ports P2 2–P20. When using the serial I/O, ports P22–P20 have the following functions:
q P20: Serial I/O synchronous clock input/output pin (SCLK)
q P21: Serial I/O data input/output pin (SOUT)
q P22: Serial I/O data input pin (SIN)
The functions of these ports can be selected by the serial I/O mode register.
The transfer clock that determines the serial data transfer rate can selected 4 kinds of clock sources with
the serial I/O mode register.
Figure 2.7.1 shows the serial I/O block diagram, Figure 2.7.2 shows the serial I/O mode register.
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7220 Group User’s Manual