TMS320F2811 datasheet(116/173 Pages) TI

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Electrical Specifications

116

April 2001 − Revised July 2007

SPRS174O

6.20

General-Purpose Input/Output (GPIO) − Input Timing

GPIO

Signal

Sampling Window

Output From

Qualifier

SYSCLKOUT

QUALPRD = 1

(SYSCLKOUT/2)

NOTES: A. This glitch is ignored by the input qualifier. The QUALPRD bit field specifies the qualification sampling period. It can vary from

00 to 0xFF. Input qualification is not applicable when QUALPRD = 00. For any other value “n”, the qualification sampling period

in 2n SYSCLKOUT cycles (i.e., at every 2n SYSCLKOUT cycle, the GPIO pin will be sampled). Six consecutive samples must

be of the same value for a given input to be recognized.

B. For the qualifier to detect the change, the input must be stable for 10 SYSCLKOUT cycles or greater. In other words, the inputs

should be stable for (5

× QUALPRD × 2) SYSCLKOUT cycles. This would enable five sampling periods for detection to occur.

Since external signals are driven asynchronously, a 13-SYSCLKOUT-wide pulse provides reliable recognition.

See Note A

Sampling period, determined by GPxQUAL

[QUALPRD]

(SYSCLKOUT cycle

y 2 y QUALPRD) y 5

Figure 6−24. GPIO Input Qualifier − Example Diagram for QUALPRD = 1

Table 6−23. General-Purpose Input Timing Requirements

MIN

MAX

UNIT

tw(GPI)

Pulse duration, GPIO low/high

All GPIOs

With no qualifier

2tc(SCO)

cycles

tw(GPI)

Pulse duration, GPIO low/high

All GPIOs

With qualifier

1tc(SCO) + IQT†

cycles

† Input Qualification Time (IQT) = [tc(SCO) × 2 × QUALPRD] × 5 + [tc(SCO) × 2 × QUALPRD].

GPIOxn

XCLKOUT

tw(GPI)

Figure 6−25. General-Purpose Input Timing

NOTE:

The pulse width requirement for general-purpose input is applicable for the XBIO and ADCSOC

pins as well.

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