LM3S3739 Luminary Micro, Inc, LM3S3739 Datasheet - Page 437

• Manufacturer Part Number: LM3S3739
• Description: Lm3s3739 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Reset
Reset
Type
Type
SSI Data (SSIDR)
SSI0 base: 0x4000.8000
SSI1 base: 0x4000.9000
Offset 0x008
Type R/W, reset 0x0000.0000
June 02, 2008
Bit/Field
31:16
15:0
R/W
RO
31
15
0
0
R/W
RO
Register 3: SSI Data (SSIDR), offset 0x008
SSIDR is the data register and is 16-bits wide. When SSIDR is read, the entry in the receive FIFO
(pointed to by the current FIFO read pointer) is accessed. As data values are removed by the SSI
receive logic from the incoming data frame, they are placed into the entry in the receive FIFO (pointed
to by the current FIFO write pointer).
When SSIDR is written to, the entry in the transmit FIFO (pointed to by the write pointer) is written
to. Data values are removed from the transmit FIFO one value at a time by the transmit logic. It is
loaded into the transmit serial shifter, then serially shifted out onto the SSITx pin at the programmed
bit rate.
When a data size of less than 16 bits is selected, the user must right-justify data written to the
transmit FIFO. The transmit logic ignores the unused bits. Received data less than 16 bits is
automatically right-justified in the receive buffer.
When the SSI is programmed for MICROWIRE frame format, the default size for transmit data is
eight bits (the most significant byte is ignored). The receive data size is controlled by the programmer.
The transmit FIFO and the receive FIFO are not cleared even when the SSE bit in the SSICR1
register is set to zero. This allows the software to fill the transmit FIFO before enabling the SSI.
30
14
0
0
R/W
RO
29
13
reserved
0
0
Name
DATA
R/W
RO
28
12
0
0
R/W
RO
27
11
0
0
Type
R/W
RO
R/W
RO
26
10
0
0
0x0000
0x0000
R/W
RO
Reset
25
0
9
0
Preliminary
R/W
RO
24
0
8
0
reserved
DATA
Description
Software should not rely on the value of a reserved bit. To provide
compatibility with future products, the value of a reserved bit should be
preserved across a read-modify-write operation.
SSI Receive/Transmit Data
A read operation reads the receive FIFO. A write operation writes the
transmit FIFO.
Software must right-justify data when the SSI is programmed for a data
size that is less than 16 bits. Unused bits at the top are ignored by the
transmit logic. The receive logic automatically right-justifies the data.
R/W
RO
23
0
7
0
R/W
RO
22
0
6
0
R/W
RO
21
0
5
0
R/W
RO
20
0
4
0
R/W
RO
19
0
3
0
LM3S3739 Microcontroller
R/W
RO
18
0
2
0
R/W
RO
17
0
1
0
R/W
RO
16
0
0
0
437