Texas Instruments SM320F2812-HT specifications Pin

SM320F2812-HT

www.ti.com SGUS062A –JUNE 2009 –REVISED APRIL 2010

Figure 4-12shows how the various register bits select the various modes of operation for GPIO function.

GPxDAT/SET/CLEAR/TOGGLE			Digital I/O	Peripheral I/O
Register Bit(s)
GPxQUAL		GPxMUX	GPxDIR	High-
				Impedance
Register		Register Bit	Register Bit
				Control
0	1		0	1
MUX			MUX
Input Qualification				SYSCLKOUT
		High-Impedance
		Enable (1)
				XRS

Internal (Pullup or Pulldown)

PIN

A.In the GPIO mode, when the GPIO pin is configured for output operation, reading the GPxDAT data register only gives the value written, not the value at the pin. In the peripheral mode, the state of the pin can be read through the GPxDAT register, provided the corresponding direction bit is zero (input mode).

B.Some selected input signals are qualified by the SYSCLKOUT. The GPxQUAL register specifies the qualification sampling period. The sampling window is 6 samples wide and the output is only changed when all samples are the same (all 0's or all 1's). This feature removes unwanted spikes from the input signal.

Figure 4-12. GPIO/Peripheral Pin Multiplexing

NOTE

The input function of the GPIO pin and the input path to the peripheral are always enabled. It is the output function of the GPIO pin that is multiplexed with the output path of the primary (peripheral) function. Since the output buffer of a pin connects back to the input buffer, any GPIO signal present at the pin is propagated to the peripheral module as well. Therefore, when a pin is configured for GPIO operation, the corresponding peripheral functionality (and interrupt-generating capability) must be disabled. Otherwise, interrupts may be inadvertently triggered. This is especially critical when the PDPINTA and PDPINTB pins are used as GPIO pins, since a value of zero for GPDDAT.0 or GPDDAT.5 (PDPINTx) puts PWM pins in a high-impedance state. The CxTRIP and TxCTRIP pins also put the corresponding PWM pins in high impedance, if they are driven low (as GPIO pins) and bit EXTCONx.0 = 1.

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