Figure 168. Spi Multi-Master Slave Environment - Holtek HT32F54231 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
Mode Fault – MF
The mode fault flag can be used to detect SPI bus usage in the SPI multi-master mode. For the
multi-master mode, the SPI module is configured as a master device and the SEL signal is set as
an input signal. The mode fault flag is set when the SPI_SEL pin is suddenly changed to an active
level by another SPI master. This means that another SPI master is requesting to use the SPI bus.
Therefore, when an SPI mode fault occurs, it will force the SPI module to operate in the slave mode
and also disable all of the SPI interface signals to avoid SPI bus signal collisions. For the same
reason, if the SPI master wants to transfer data, it also needs to inform other SPI masters by driving
their SEL signals to an active state. The detailed configuration diagram for the SPI multi-master
mode is shown in the following figure.
Master

Figure 168. SPI Multi-Master Slave Environment

Rev. 1.00
SCK
MOSI
SPI
MISO
SEL
I/O 0
I/O 1
I/O 2
454 of 576
SCK
MOSI
SPI
Master
MISO
SEL
I/O 0
I/O 1
I/O 2
SCK
MOSI
SPI
Slave
MISO
SEL
SCK
MOSI
SPI
Slave
MISO
SEL
January 28, 2022