| I2CSTART | Example |
I2CSTART Pin
Function
Generates an I2C Start condition.
Quick Facts
| SX18/20 | SX28 | SX48 | SX52 | |
| SDA pin | RA.0 .. RA.2 RB.0 .. RB.6 |
RA.0 .. RA.2 RB.0 .. RB.6 RC.0 .. RC.6 |
RA.0 .. RA.2 RB.0 .. RB.6 RC.0 .. RC.6 RD.0 .. RD.6 RE.0 .. RE.6 |
RA.0 .. RA.6 RB.0 .. RB.6 RC.0 .. RC.6 RD.0 .. RD.6 RE.0 .. RE.6 |
| SCL pin | Next pin in same group as SDA assignment. | |||
| Transmission rate | Approximately 50 kBits/sec. | |||
| Special Notes | Both the SDA and SCL pins must have 4.7 kΩ pull-up resisters. | |||
Explanation
The I2C protocol is a form of synchronous serial communication developed by
Philips Semiconductor. It only requires two I/O pins and both pins can be shared
between multiple I2C devices. The I2CSTART instruction generates an I2C
Start condition on the I2C bus (SDA and SCL pins); this condition is used to
start (or restart) a transmission sequence.
Note that the SCL pin is automatically assigned to the next higher pin in the same group as the SDA pin, so the SDA pin may not be assigned to RA.3 (RA.6 on the SX52), RB.7, RC.7, RD.7, or RE.7.
Special Note
The I2CSTART instruction monitors the state of the SCL line and will
wait for SCL to be high before returning; this could cause some systems to
hang if the SCL line is shorted to Vss. To prevent this hang, the programmer
can make the SCL line an input then test its state before calling I2CSTART.