Network SSP Serial Port

Figure 16-10. Programmable Serial Protocol (single transfers)

SSPSCLK

 

 

 

 

(when SCMODE = 0)

 

 

 

 

SSPSCLK

 

 

 

 

(when SCMODE = 1)

 

 

 

 

SSPSCLK

 

 

 

 

(when SCMODE = 2)

 

 

 

 

SSPSCLK

 

 

 

 

(when SCMODE = 3)

 

 

 

 

SSPTXD

Undefined

MSB

LSB

End of Transfer

Data State

T1

T2

T3

 

T4

SSPRXD

Undefined

MSB

LSB

Undefined

SSPSFRM

 

 

 

 

(when SFRMP = 1)

 

 

 

 

SSPSFRM

T5

T6

 

 

 

 

 

 

(when SFRMP = 0)

 

 

 

 

A9522-02

Table 16-2. Programmable Serial Protocol (PSP) Parameters

 

 

 

 

 

 

 

Symbol

Definition

Range

Units

 

 

 

 

 

 

 

 

(Drive, Sample, SSPSCLK Idle)

 

 

 

Serial clock mode

0 - Fall, Rise, Low

 

 

1 - Rise, Fall, Low

 

(SSPSP[SCMODE])

 

 

2 - Rise, Fall, High

 

 

 

 

 

 

 

 

3 - Fall, Rise, High

 

 

 

 

 

 

 

Serial frame polarity

High or Low

 

(SSPSP[SFRMP])

 

 

 

 

 

 

 

 

 

 

T1

Start delay

0 - 7

Clock period

 

(SSPSP[STRTDLY])

 

 

 

 

 

 

 

 

 

 

T2

Dummy start

0 - 3

Clock period

 

(SSPSP[DMYSTRT])

 

 

 

 

 

 

 

 

 

 

T3

Data size

4 - 32

Clock period

 

(SSCR0[EDSS] and SSCR0[DSS])

 

 

 

 

 

 

 

 

 

 

T4

Dummy stop (SSPSP[DMYSTOP])

0 - 3

Clock period

 

 

 

 

 

 

T5

SSPSFRM delay (SSPSP[SFRMDLY]

0 - 88

Half clock period

 

 

 

 

 

 

T6

SSPSFRM width (SSPSP[SFRMWDTH]

1 - 44

Clock period

 

 

 

 

 

 

 

End of transfer data state (SSPSP[ETDS])

Low or [bit 0]

 

 

 

 

 

Note: The SSPSFRM delay must not extend beyond the end of T4. SSPSFRM Width must be asserted for at least 1 SSPSCLK, and must be deasserted before the end of the T4 cycle (i.e. in terms of time, not bit values, (T5 + T6) <= (T1 + T2 + T3 + T4), 1<= T6 < (T2 + T3 + T4), and (T5 + T6) >= (T1

+1) to ensure that SSPSFRM is asserted for at least 2 edges of the SSPSCLK). While the PSP can be programmed to generate the assertion of SSPSFRM during the middle of the data transfer (after the MSB was sent), the SSP is not able to receive data in frame slave mode (SSCR1[SFRMDIR] is

16-12

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Programmable Serial Protocol PSP Parameters, Sspspscmode, Sspspsfrmp, Sspspstrtdly, Sspspdmystrt