ST72321AR6-Auto STMicroelectronics, ST72321AR6-Auto Datasheet - Page 124

• Manufacturer Part Number: ST72321AR6-Auto
• Description: 8-bit MCU for automotive with 32 Kbyte Flash, 10-bit ADC, timers, SPI, SCI and I2C interfaces
• Manufacturer: STMicroelectronics

Specifications of ST72321AR6-Auto

• Hdflash Endurance: 100 cycles, data retention 20 years
• Clock Sources: crystal/ceramic resonator oscillators, internal RC oscillator and bypass for external clock
• 4 Power Saving Modes: Halt, Active Halt, Wait and Slow

Serial peripheral interface (SPI)
14.3.3
Note:
Note:
Note:
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Figure 57. Generic SS timing diagram
Figure 58. Hardware/Software slave select management
Master mode operation
In master mode, the serial clock is output on the SCK pin. The clock frequency, polarity and
phase are configured by software (refer to the description of the SPICSR register).
The idle state of SCK must correspond to the polarity selected in the SPICSR register (by
pulling up SCK if CPOL = 1 or pulling down SCK if CPOL = 0).
How to operate the SPI in master mode
To operate the SPI in master mode, perform the following steps in order:
1.
The slave must have the same CPOL and CPHA settings as the master.
2.
3.
MSTR and SPE bits remain set only if SS is high).
IMPORTANT: If the SPICSR register is not written first, the SPICR register setting (MSTR
bit) may not be taken into account.
The transmit sequence begins when software writes a byte in the SPIDR register.
MOSI/MISO
(if CPHA=0)
(if CPHA=1)
Master SS
Write to the SPICR register:
a)
b)
Write to the SPICSR register:
Either set the SSM bit and set the SSI bit or clear the SSM bit and tie the SS pin high
for the complete byte transmit sequence.
Write to the SPICR register:
Set the MSTR and SPE bits
Slave SS
Slave SS
Select the clock frequency by configuring the SPR[2:0] bits.
Select the clock polarity and clock phase by configuring the CPOL and CPHA bits.
Figure 59
shows the four possible configurations.
SS external pin
SSI bit
Doc ID 13829 Rev 1
Byte 1
SSM bit
1
0
Byte 2
SS internal
Byte 3
ST72321xx-Auto