263
CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
μ
PD78018F SUBSERIES)
(1) Serial I/O shift register 0 (SIO0)
This 8-bit register converts parallel data into serial data, and transmits/receives serial data (shift operation)
in synchronization with the serial clock.
SIO0 is set by an 8-bit memory manipulation instruction.
When the bit 7 (CSIE0) of the serial operation mode register 0 (CSIM0) is 1, the serial operation is started
when data is written to SIO0.
The data written to SIO0 is output to the serial output line (SO0) or serial data bus (SB0/SB1) for transmission.
When data is received, it is read from the serial input line (SI0) or SB0/SB1 to SIO0.
In the SBI mode and 2-wire serial I/O mode bus configuration, the input and output pins are shared. Therefore,
the device that is to receive data must write FFH to SIO0 in advance (except, however, when an address is
received by setting 1 to bit 5 (WUP) of CSIM0).
In the SBI mode, the busy status can be released by writing data to SIO0. In this case, bit 7 (BSYE) of the
serial bus interface control register (SBIC) is not cleared to 0.
The contents of SIO0 become undefined when the RESET signal is input.
(2) Slave address register (SVA)
This 8-bit register sets the value of a slave address when the microcontroller is connected to the serial bus
as a slave device. It is not used in the 3-wire serial I/O mode.
SVA is set by an 8-bit memory manipulation instruction.
The master outputs a slave address to the slaves connected to it, to select a specific slave. The slave address
output by the master and the value of the SVA are compared by an address comparator. If the two addresses
coincide, the slave is selected. At this time, bit 6 (COI) of the serial operation mode register 0 (CSIM0) is set
to 1.
The high-order 7 bits of data with its LSB masked by setting the bit 4 (SVAM) of the interrupt timing specification
register (SINT) can also compare the slave address.
If no coincidence is detected when the address is received, bit 2 (RELD) of the serial bus interface control
register (SBIC) is cleared to 0.
The wake-up function can be used by setting bit 5 (WUP) of CSIM0 to 1 in the SBI mode. In this case, an
interrupt request signal (INTCI0) is generated only when the slave address output by the master coincides
with the value of SVA. This is interrupt signal indicates that the master requests communication. If bit 5 (SIC)
of the interrupt timing specification register (SINT) is set to 1, the wake-up function cannot be used even if
WUP is set to 1 (the interrupt request signal is generated on detection of bus release). Clear SIC to 0 when
using the wake-up function.
When the microcontroller transmits data as the master or a slave in the SBI mode or 2-wire serial I/O mode,
errors can be detected by using SVA.
The contents of SVA become undefined when the RESET signal is input.