LM3S2139 Luminary Micro, Inc, LM3S2139 Datasheet - Page 325

• Manufacturer Part Number: LM3S2139
• Description: Lm3s2139 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

13.4
Table 13-1. SSI Register Map
July 25, 2008
Offset
0x000
Name
SSICR0
4.
5.
As an example, assume the SSI must be configured to operate with the following parameters:
■
■
■
■
Assuming the system clock is 20 MHz, the bit rate calculation would be:
FSSIClk = FSysClk / (CPSDVSR * (1 + SCR))
1x106 = 20x106 / (CPSDVSR * (1 + SCR))
In this case, if CPSDVSR=2, SCR must be 9.
The configuration sequence would be as follows:
1.
2.
3.
4.
5.
Register Map
Table 13-1 on page 325 lists the SSI registers. The offset listed is a hexadecimal increment to the
register’s address, relative to that SSI module’s base address:
■
Note:
Master operation
Freescale SPI mode (SPO=1, SPH=1)
1 Mbps bit rate
8 data bits
SSI0: 0x4000.8000
Write the SSICR0 register with the following configuration:
■
■
■
■
Enable the SSI by setting the SSE bit in the SSICR1 register.
Ensure that the SSE bit in the SSICR1 register is disabled.
Write the SSICR1 register with a value of 0x0000.0000.
Write the SSICPSR register with a value of 0x0000.0002.
Write the SSICR0 register with a value of 0x0000.09C7.
The SSI is then enabled by setting the SSE bit in the SSICR1 register to 1.
Serial clock rate (SCR)
Desired clock phase/polarity, if using Freescale SPI mode (SPH and SPO)
The protocol mode: Freescale SPI, TI SSF, MICROWIRE (FRF)
The data size (DSS)
The SSI must be disabled (see the SSE bit in the SSICR1 register) before any of the control
registers are reprogrammed.
Type
R/W
0x0000.0000
Reset
Preliminary
Description
SSI Control 0
LM3S2139 Microcontroller
page
See
327
325