Texas Instruments MSP50C614 manual Dedicated Input Port F

I/O

3.1.2Dedicated Input Port F

Port F is an 8-bit wide input-only port. The data presented to the input pin can be read by referring to the appropriate bit in the F port data register, address 0x28. This is done using the IN instruction, with the 0x28 address as an argument. The state of the F port data registers after RESET low is unknown (input state provided by external hardware)

Each of the pins at port F has a programmable pull-up resistor. The resistance of these pullups is at least 100 kΩ. All eight pullup resistors can be enabled by setting the enable pullup (EP) in the interrupt/general control register (Int- GenCtrl). The address of the IntGenCtrl is 0x38, and the location of the EP bit is 12. Clearing the EP bit disables the eight pullups, and setting the EP bit en- ables the eight pullups. After RESET low, the default setting for the EP bit is 0 (F-port pullups disabled).

	Input Port F
Data register address	0x28h
Possible input data values	Low = 0 High = 1
Possible output data values	N/A
Value after RESET low	Pullup resistors DISABLED

When reading from the 8-bit F-port data register to a 16-bit accumulator, the IN instruction automatically clears the extra bits in excess of 8. The desired bits in the result will be right-justified within the accumulator.

The following table shows the bit locations of the port F address mapping:

F port Input Data register
address 0x28h	(8-bit wide location)
READ only	07 06 05 04 03 02 01 00
	F7 F6 F5 F4 F3 F2 F1 F0

The external interrupt INT5 is triggered by a falling-edge event on any of the eight port-F input pins (see Section 3.1.5, Internal and External Interrupts). Specifically, INT5 is triggered if all eight port-F pins are held high, and then one or more of these pins is taken low. Port F, therefore, is especially useful as a key-scan interface.

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