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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
873
Synchronous Serial Port—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
For outbound data transfers (WRITE from system to SSP peripheral), the register may
be loaded (written) by the system processor anytime it is empty.
When a data size of less than 16-bits is selected, the user should not left-justify data
written to the transmit FIFO. Transmit logic left-justifies the data and ignores any
unused bits. Received data less than 16-bits is automatically right-justified in the
receive buffer. When the SSP is programmed for National Microwire frame format, the
default size for transmit data is 8-bits (the most significant byte is ignored), the receive
data size is controlled by the programmer using the DSS field in SSCR0.
The following table shows the location of the SSP data register. Note that both FIFOs
are cleared when the block is reset, or by writing a zero to SSE (SSP disabled).
Register Name:
SSDR
Block
Base Address:
0xC801_20
Offset Address
0x10
Reset Value
0x0000_0000
Register Description:
SSP Data Register
Access:
(See below.)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
Reserved
Data
Register
SSDR
Bits
Name
Description
Reset Value
Access
31:16
(Reserved)
(Reserved)
0x0000
15:00
Data
Data (Low Word): Data word to be written to/read from the Transmit/
Receive FIFO
0x0000