Texas Instruments MSP50C614 General-Purpose I/O Ports, Port a Port B Port C Port D Port E

I/O

3.1 I/O

The C614 has 64 input-output pins. Forty of these are software configurable as either inputs or outputs. Eight are dedicated inputs, and the remaining sixteen are dedicated outputs.

3.1.1General-Purpose I/O Ports

The forty configurable input/output pins are organized in 5 ports, A,B,C,D, and E. Each port is one byte wide. The pins within these ports can be individually programmed as input or output, in any combination. The selection is made by clearing or setting the appropriate bit in the associated control register (Control A, B, C, D, or E). Clearing the bit in the control register renders the pin as a high-impedance input. Setting the control bit renders the pin as a totem-pole- output.

When configured as an input, the data presented to the input pin can be read by referring to the appropriate bit in the associated data register (Data A, B, C, D, or E). This is done using the IN instruction, with the address of the data register as an argument.

When configured as an output, the data driven by the output pin can be controlled by setting or clearing the appropriate bit in the associated data register. This is done using the OUT instruction, with the address of the data register as an argument.

	Port A	Port B	Port C		Port D	Port E
Control register address	0x04h²	0x0Ch	0x14h		0x1Ch	0x24h
Possible control values	0 = High-Z INPUT		1 = TOTEM-POLE OUTPUT
Value after RESET low		0 = High-Z INPUT
Data register address	0x00h	0x08h	0x10h		0x18h	0x20h
Possible input data values	Low = 0 High = 1			(don't care on write)
Possible output data values		0 = Low		1 = High

²Each of these I/O ports is only 8 bits wide. The reason for the 4-byte address spacing is so that instructions with limited addressability (such as memory transfers) can still access these registers.

Note: Reading the Data Register

Whether configured as input or as output, reading the data register reads the actual state of the pin.

The programmable I/O are initialized to a known state by cycling the RESET pin low-to-high. The state of the control registers during and after RESET low

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