12F683 Physical Input and Output

The 12F683 has 6 I/O pins

These pins are accessed via the GPIO port

To identify which bit within the port is responsible for driving a particular PIC pin, look at the pin diagram below (this diagram is only good for the 12F683, refer to other pin diagrams for other PICs). Locate the pin you are interested in and read off the label.

The label will be of the form GPj

where j will be the bit number within the port (in the range 0 to 7)

On the 12F683 the GPIO port bit 0 connects to the pin labelled GP0 which is pin 7, the GPIO port bit 3 connects to the pin labelled GP3 which is pin 4

NOTE: most of the I/O pins on the 12F683 have multiple functions and multiple labels to indicate these functions. When using a pin it must be configured to perform the required function. This is done internally by the program when it starts running. The program writes to special function registers which are responsible for configuring the pins.

LABEL PIN   PIN DIAGRAM
 
GP0 7            12f683 pin diagram
GP16
GP25
GP34
GP43
GP52
sample projects (ciruits, sample code and chip programming)

XCSB compiler

Writing to a specific pin

To write to pin 5 of a 12F683 lookup the label on pin 5 in the pin diagram. The label is GP2. This translates to GP bit 2.

BIT NUMBER    7 6 5 4 3 2 1 0
GPIO x x x x x x x x
TRISIO x x x x x x x x
PIN LABEL      GP7     GP6     GP5     GP4     GP3     GP2     GP1     GP0  
PIN NUMBER N/A N/A 2 3 4 5 6 7

Clear the corresponding bit in the GP data direction register (called TRISIO) to 0, that is clear TRISIO bit 2 to 0. This configures pin 5 as an output.

BIT NUMBER    7 6 5 4 3 2 1 0
GPIO x x x x x x x x
TRISIO x x x x x 0 x x
PIN LABEL      GP7     GP6     GP5     GP4     GP3     GP2     GP1     GP0  
PIN NUMBER N/A N/A 2 3 4 5 6 7

Then write the required value (0 or 1) to GPIO bit 2

BIT NUMBER    7 6 5 4 3 2 1 0
GPIO x x x x x 0 or 1 x x
TRISIO x x x x x 0 x x
PIN LABEL      GP7     GP6     GP5     GP4     GP3     GP2     GP1     GP0  
PIN NUMBER N/A N/A 2 3 4 5 6 7

This can be done in XCSB as: 

// configure pin 5 as output by writing 0 to TRISIO bit 2
TRISIO = TRISIO & ~0x04

// set pin 5 low (to 0) by writing 0 to GPIO bit 2
GPIO = GPIO & ~0x04

// set pin 5 high (to 1) by writing 1 to GPIO bit 2
GPIO = GPIO | 0x04
The 0x04 value is a hex mask (the equivalent of binary 00000100 see binary to hex).

A simpler way to access a bit within a byte is to use a constant expression of the form 

	(1 << n)
where n is the bit number and << is the left shift operator

To access multiple bits within a byte, combine them with the bit wise OR operator
e.g. 

	(1 << n) | (1 << m) | (1 << j)
where n, m and j are the bit numbers

To set pins 1 and 7 to 1 use 

TRISIO = TRISIO & ~((1 << 2) | (1 << 0))
GPIO = GPIO | ((1 << 2) | (1 << 0))
More about bit manipulation and binary

Reading from a specific pin

To read from pin 5 of a 12F683 lookup the label on pin 5 in the pin diagram. The label is GP2. This translates to GP bit 2.

BIT NUMBER    7 6 5 4 3 2 1 0
GPIO x x x x x x x x
TRISIO x x x x x x x x
PIN LABEL      GP7     GP6     GP5     GP4     GP3     GP2     GP1     GP0  
PIN NUMBER N/A N/A 2 3 4 5 6 7

Set the corresponding bit in the GP data direction register (called TRISIO) to 1, that is set TRISIO bit 2 to 1. This configures pin 5 as an input.

BIT NUMBER    7 6 5 4 3 2 1 0
GPIO x x x x x x x x
TRISIO x x x x x 1 x x
PIN LABEL      GP7     GP6     GP5     GP4     GP3     GP2     GP1     GP0  
PIN NUMBER N/A N/A 2 3 4 5 6 7

Then read from GP and mask out bit 2

This can be done in XCSB as: 

// configure pin 5 as input by writing 1 to TRISIO bit 2
TRISIO = TRISIO | 0x04

// read 0 or 1 into the variable called result
result = (GPIO & 0x04) != 0

// NOTE: the expression (GPIO & 0x04) return 0x00 or 0x04
// the expression X != 0 return 0 if X is 0x00 or 1 if X is 0x04
The 0x04 value is a hex mask (the equivalent of binary 00000100 see binary to hex).

A simpler way to access a bit within a byte is to use a constant expression of the form 

	(1 << n)
where n is the bit number and << is the left shift operator

The above example could then be re-written as: 

// configure pin 5 as input by writing 1 to TRISIO bit 2
TRISIO = TRISIO | (1 << 2)

// read 0 or 1 into the variable called result
result = (GPIO & (1 << 2)) != 0

// NOTE: the expression (GPIO & (1 << 2)) return 0x00 or 0x04
// the expression X != 0 return 0 if X is 0x00 or 1 if X is 0x04

More about bit manipulation and binary