SPEAR1340 datasheet(152/200 Pages) STMICROELECTRONICS

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Timing characteristics

SPEAr1340

152/200

Doc ID 023063 Rev 4

5.2

ADC timing characteristics

This section describes the timing characteristics of the TOUCH_XY_SEL signal of the A/C

converter.

The TOUCH_XY_SEL signal allows the switching of the X and Y axes. It is generated in

both cases of 2 and 4 channels (depending on single or dual touchscreen configuration).

This signal is high when converting the X values, while low when converting the Y ones.

Figure 16 shows the TOUCH_XY_SEL behavior during the ADC conversion phase. In this

example, the dual touchscreen configuration is used: channels 1 and 3 convert the X values,

while channels 6 and 7 convert the Y values.

Figure 16.

Touchscreen signal waveform

5.3

Cortex-A9 JTAG/trace timing characteristics

This section describes the timing characteristics of Cortex-A9 JTAG and Cortex-A9 trace.

5.3.1

Cortex-A9 JTAG timing characteristics

This section describes the timing characteristics for the Cortex-A9 JTAG.

The timing characterization is performed assuming an output load capacitance of 20 pF on

ARM_TDO output and an input transition of 2 ns on all the inputs.

Figure 17.

JTAG timing waveforms

ADC_CLK

ADC_EN

ADC_SEL

TOUCH_XY_SEL

ARM_TCK (input)

ARM_TDO (output)

TCLKhigh

TCLKlow

TDmin

ARM_TDI, ARM_TMS,

ARM_TRSTn (input)

Old data valid

New data valid

TDmax

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