
18.4 Functions
18.4.1
Low Power Consumption Function
The serial bus interface has a low power consumption register (POFFCR1) that saves power when the serial
bus interface is not being used.
Setting POFFCR1<SBI0EN> to "0" disables the basic clock supply to the serial bus interface to save power.
Note that this makes the serial bus interface unusable. Setting POFFCR1<SBI0EN> to "1" enables the basic clock
supply to the serial bus interface and makes external interrupts usable.
After reset, POFFCR1<SBI0EN> is initialized to "0", and this makes the serial bus interface unusable. When
using the serial bus interface for the first time, be sure to set POFFCR1<SBI0EN> to "1" in the initial setting of
the program (before the serial bus interface control registers are operated).
Do not change POFFCR1<SBI0EN> to "0" during the serial bus interface operation, otherwise serial bus
interface may operate unexpectedly.
18.4.2
Selecting the slave address match detection and the GENERAL CALL detection
SBI0CR1<NOACK> enables and disables the slave address match detection and the GENERAL CALL de-
tection in the slave mode.
Clearing SBI0CR1<NOACK> to "0" enables the slave address match detection and the GENERAL CALL
detection.
Setting SBI0CR1<NOACK> to "1" disables the subsequent slave address match and GENERAL CALL de-
tections. The slave addresses and "GENERAL CALL" sent from the master are ignored. No acknowledgement
is returned and no interrupt request is generated.
In the master mode, SBI0CR1<NOACK> is ignored and has no influence on the operation.
Note:If SBI0CR1<NOACK> is cleared to "0" during data transfer in the slave mode, it remains at "1" and returns
an acknowledge signal of data transfer.
18.4.3
Selecting the number of clocks for data transfer and selecting the acknowledge-
ment or non-acknowledgment mode
1-word data transfer consists of data and an acknowledge signal. When the data transfer is finished, an interrupt
request is generated.
SBI0CR1<BC> is used to select the number of bits of data to be transmitted/received subsequently.
The acknowledgment mode is activated by setting SBI0CR1<ACK> to "1".
The master device generates the clocks for an acknowledge signal and outputs an acknowledge signal in the
receiver mode. The slave device counts the clocks for an acknowledge signal and outputs an acknowledge signal
in the receiver mode.
The non-acknowledgment mode is activated by setting SBI0CR1<ACK> to "0".
The master device does not generate the clocks for an acknowledge signal. The slave device does not count
the clocks for an acknowledge signal.
18.4.3.1
Number of clocks for data transfer
The number of clocks for data transfer is set by using SBI0CR1<BC> and SBI0CR1<ACK>.
The acknowledgment mode is activated by setting SBI0CR1<ACK> to "1".
TMP89FH42
18. Serial Bus Interface (SBI)
18.4 Functions
Page 282
RA002