PD72042B_15 Datasheet, PDF (24/92 Pages) Renesas Technology Corp – LSI DEVICE FOR Inter Equipment BusTM (IEBusTM) PROTOCOL CONTROL

µPD72042B
3. MICROCOMPUTER INTERFACE
3.1 TRANSFER METHOD
Either of two microcomputer interface modes can be selected: three-wire serial I/O mode or two-wire serial I/O
mode.
Whether three-wire serial I/O mode or two-wire serial I/O mode is selected depends on the input level of the SEL
pin (pin 12). (See Section 3.3 for details.)
SEL ← 1: Three-wire serial I/O
SEL ← 0: Two-wire serial I/O
(1) Three-wire serial I/O (SEL ← 1)
Three wires are used to read and write data. The three wires are the serial clock input (SCK), serial data input
(SI^{Note 1}), and serial data output (SO^{Note 2}).
(a) Read operation
Data is output to the SO pin upon detecting the falling edge of the SCK pin.
(b) Write operation
Data is input via the SI pin upon detecting the rising edge of the SCK pin. At this time, 1 is output on the
SO pin.
(2) Two-wire serial I/O (SEL ← 0)
Two wires are used to read and write data. The two wires are the serial clock input (SCK) and serial data I/O
(SIO^{Note 1}).
(a) Read operation
The SIO pin is placed in the output state, and data is output upon detecting the falling edge of the SCK pin.
(b) Write operation
The SIO pin is placed in the input state, and data is input upon detecting the rising edge of the SCK pin.
Notes 1. The SI pin for three-wire serial I/O mode is also used as the SIO pin for two-wire serial I/O mode.
2. The impedance of the SO pin for three-wire serial I/O mode goes high in two-wire serial I/O mode. So,
connect the SO pin to GND or VDD.
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Data Sheet S13990EJ3V0DS