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8-6 Intel® PXA255 Processor Developer’s Manual
Synchronous Serial Port Controller
Figure 8-3 shows the National Microwire frame format with 8-bit command words for single and
back-to-back frame transmissions.
8.4.2 Parallel Data Formats for FIFO Storage
Data in the FIFOs is stored with one 16-bit value per data sample with no regard to the format’s
data word length. In each 16-bit field, the stored data sample is right-justified, the word’s least
significant bit is stored in bit 0, and unused bits are packed as zeroes above the most significant bit.
Logic in the SSPC automatically left-justifies data in the Transmit FIFO so the sample is properly
transmitted on SSPTXD in the selected frame format.
Figure 8-3. National Microwire* Frame Format
SSPSCLK
... ...
SSPSFRM
... ...
SSPTXD Bit<7> ... Bit<0> ...
8-Bit Control 1 Clk
SSPRXD ... Bit<N> ... Bit<0>
4 to 16 Bits
Single Transfer
SSPSCLK
... ... ...
SSPSFRM
... ... ...
SSPTXD Bit<0> ... Bit<7> ... Bit<0> ...
1 Clk 1 Clk
SSPRXD Bit<N> ... Bit<0> ... Bit<N> ... Bit<0>
Continuous Transfers