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ISD91200 Series Technical Reference Manual
Release Date: Sep 16, 2019
- 219 -
Revision 2.4
5.9.4
SPI0 Function Descriptions
5.9.4.1
SPI Engine Clock and SPI Serial Clock
The SPI controller derives its clock source from the system HCLK as determined by the CLKSEL1
register. The frequency of the SPI master clock is determined by the divisor ratio SPI0_CLKDIV.
In Master mode, the output frequency of the SPI serial clock output pin is equal to the SPI engine clock
rate. In general, the SPI serial clock is denoted as SPI clock. In Slave mode, the SPI serial clock is
provided by an off-chip master device. The SPI engine clock rate of slave device must be faster than
the SPI serial clock rate of the master device. The frequency of SPI engine clock cannot be faster than
the APB clock rate regardless of Master or Slave mode.
5.9.4.2
Master/Slave Mode
This SPI0 controller can be configured as in master or slave mode by setting the SLAVE bit
(SPI0_CTL.SLAVE). In master mode the I91200 generates SCLK and SSB signals to access one or
more slave devices. In slave mode the I91200 monitors SCLK and SSB signals to respond to data
transactions from an off-chip master. The signal directions are summarized in the application block
diagrams.
ISD91200
SPI Controller
Master
SCLK
MISO
MOSI
SSB0
SSB1
SCLK
MISO
MOSI
SS
Slave 0
SCLK
MISO
MOSI
SS
Slave 1
Figure 5-35 SPI Master Mode Application Block Diagram
ISD91200
SPI Controller
Slave
SCLK
MISO
MOSI
SSB0
SSB1
SCLK
MISO
MOSI
SS
Master
Figure 5-36 SPI Slave Mode Application Block Diagram