User manual
SSI Registers
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20.7.1.1 CR0 Register (Offset = 0h) [reset = X]
CR0 is shown in Figure 20-13 and described in Table 20-3.
Control 0
Figure 20-13. CR0 Register
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
RESERVED
R-X
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
SCR SPH SPO FRF DSS
R/W-X R/W-X R/W-X R/W-X R/W-X
Table 20-3. CR0 Register Field Descriptions
Bit Field Type Reset Description
31-16 RESERVED R X
Software should not rely on the value of a reserved. Writing any
other value than the reset value may result in undefined behavior.
15-8 SCR R/W X
Serial clock rate: This is used to generate the transmit and receive
bit rate of the SSI. The bit rate is (SSI's clock
frequency)/((SCR+1).CPSR.CPSDVSR). SCR is a value from 0-255.
7 SPH R/W X
CLKOUT phase (Motorola SPI frame format only) This bit selects the
clock edge that captures data and enables it to change state. It has
the most impact on the first bit transmitted by either permitting or not
permitting a clock transition before the first data capture edge.
0h = 1ST_CLK_EDGE : Data is captured on the first clock edge
transition.
1h = 2ND_CLK_EDGE : Data is captured on the second clock edge
transition.
6 SPO R/W X
CLKOUT polarity (Motorola SPI frame format only)
0h = SSI produces a steady state LOW value on the CLKOUT pin
when data is not being transferred.
1h = SSI produces a steady state HIGH value on the CLKOUT pin
when data is not being transferred.
5-4 FRF R/W X
Frame format. The supported frame formats are Motorola SPI, TI
synchronous serial and National Microwire. Value 0'b11 is reserved
and shall not be used.
0h = Motorola SPI frame format
1h = TI synchronous serial frame format
2h = National Microwire frame format
3-0 DSS R/W X
Data Size Select. Values 0b0000, 0b0001, 0b0010 and 0b0011 are
reserved and shall not be used.
3h = 4_BIT : 4-bit data
4h = 5_BIT : 5-bit data
5h = 6_BIT : 6-bit data
6h = 7_BIT : 7-bit data
7h = 8_BIT : 8-bit data
8h = 9_BIT : 9-bit data
9h = 10_BIT : 10-bit data
Ah = 11_BIT : 11-bit data
Bh = 12_BIT : 12-bit data
Ch = 13_BIT : 13-bit data
Dh = 14_BIT : 14-bit data
Eh = 15_BIT : 15-bit data
Fh = 16_BIT : 16-bit data
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Synchronous Serial Interface (SSI) SWCU117A–February 2015–Revised March 2015
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