TMP320C2811PBKA datasheet(104/147 Pages) TI

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Electrical Specifications

104

June 2004

SPRS257

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

GPIO

Signal

Sampling Window

QUALPRD

Output From

Qualifier

SYSCLKOUT

QUALPRD = 1

(2 x SYSCLKOUT cycles) x 5

NOTES: A. This glitch will be 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 should be stable for 10 SYSCLKOUT cycles or greater. In other words, the inputs

should be stable for (5 x QUALPRD x 2) SYSCLKOUT cycles. This would ensure six sampling windows for detection to occur.

Since external signals are driven asynchronously, an 11-SYSCLKOUT-wide pulse ensures reliable recognition.

See Note A

Figure 6−19. GPIO Input Qualifier − Example Diagram for QUALPRD = 1

Table 6−19. General-Purpose Input Timing Requirements

MIN

MAX

UNIT

t G

Pulse duration GPIO low/high

All GPIOs

With no qualifier

2 * tc(SCO)

cycles

tw(GPI)

Pulse duration, GPIO low/high

All GPIOs

With qualifier

1 * tc(SCO) + IQT†

cycles

† Input Qualification Time (IQT) = [5 x QUALPRD x 2] * tc(SCO)

GPIOxn

XCLKOUT

tw(GPI)

Figure 6−20. 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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