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16-10 Intel® PXA255 Processor Developer’s Manual
Network SSP Serial Port
Note: When configured master the SSP continues to drive SSPTXD with the last bit of data sent (the
LSB) or it drives zero, depending on the status of SSPSP[ETDS]. If SSCR0[SSE] is cleared,
SSPTXD goes low. The state of SSPRXD is undefined before the MSB and after the LSB is
transmitted. For minimum power consumption, this pin must not float.
Note: When configured master the SSP continues to drive SSPTXD with the last bit of data sent (the
LSB) or it drives zero, depending on the status of SSPSP[ETDS]. If SSCR0[SSE] is cleared,
SSPTXD goes low. The state of SSPRXD is undefined before the MSB and after the LSB is
transmitted. For minimum power consumption, this pin must not float.
16.4.3.4 PSP Details
The PSP provides programmability for several parameters that determine the transfer timings
between data.
There are four possible serial clock sub-modes, depending on the SSPSCLK edges selected for
driving data and sampling received data and the selection of idle state of the clock.
For the PSP, the idle and disable modes of the SSPTXD, SSPSCLK, and SSPSFRM are
programmable via SSPSP[ETDS], SSPSP[SCMODE] and SSPSP[SFRMP]. When transmit data is
ready, the SSPSCLK remains in its idle state for the number of serial clock (SSPSCLK) clock
periods programmed within the start delay (SSPSP[STRTDLY]) field. SSPSCLK then starts
toggling, SSPTXD remains in the idle state for the number of cycles programmed within the
dummy start field (SSPSP[DMYSTRT]). The SSPSFRM signal asserts after the number of half-
Figure 16-7. National Semiconductor Microwire
*
Frame Protocol (multiple transfers)
Figure 16-8. National Semiconductor Microwire
*
Frame Protocol (single transfers)
A9653-01
SSPSCLK
SSPSFRM
SSPTX/RX
Bit[0]
Bit[7] or
Bit[15]
Bit[0]Bit[1]
SSPTX/RX
Bit[N] Bit[0] Bit[N]
Undefined Undefined Undefined
A9521-02
SSPRXD
SSPSFRM
SSPSCLK
SSPTXD
4 to 32 Bits
Bit[7] or
Bit[15]
8 or 16-Bit Control
Bit[0]
Bit[N]
Bit[0]
End of Transfer Data State
UndefinedUndefinedUndefined