Calibre UK PICA93LV User Manual

Issue 1.3

 

Page 8

22/07/99

4.2.2.

I2C Status Checking Routine

Function definition:

int getstatus(void)

Usage:

i2cstatus = getstatus();

Function:

function to read status register of the Parallel I2C Communications Adapter.

Parameters are:

None

Value Returned:

where i2cstatus is an integer from 0x00 to 0xFF which indicates the current
status of Parallel I2C Communications Adapter. See Appendix A for details of
the status values returned.

I2C status on exit:

the status of the Parallel I2C Communications Adapter will not be affected by
using the getstatus function.

Example Usage: (see also sample programs)

main()

{

int i2cstatus;

i2ctatus = getstatus ();

printf("Parallel I2C Communications Adapter Status = %x\n", i2cstatus);

}

/*This will read the Parallel I2C Communications Adapter's current status*/

4.2.3.

I2C Address and Start Sending Routine

Function definition:

int sendaddress (int slaveaddress, int setnack)

Usage:

i2cstatus = sendaddress(slaveaddress, setnack)

Function:

This is the procedure to send Start and slave address of device which is to be
communicated with.

Parameters are:

The 8 bit slave address of the device which is to be communicated with. This
will be an even number if the adapter is to write to the slave, add 1 to get an
odd number if the adapter is to read from the slave.

This controls whether the Parallel I2C Communications Adapter transmits an
Acknowledge down the I2C Bus on reception of a byte. The last byte received
during a transfer must not be acknowledged. If setnack = 0 then acknowledge
is enabled, if setnack = 1 then acknowledge is disabled. Therefore, if a read
(odd numbered) address is being sent AND only 1 byte is to be read, setnack
should be set = 1; in all other cases it must be clear = 0.

Value Returned:

The value returned depends on whether the Start and address were sent.

If the start and address have been sent then the status returned will either be
0x00 (bus busy data sent and acknowledged), or 0x08 (bus busy, data sent
but not acknowledged).

If the start or the address cannot be sent (either the bus remained busy or the
address did not get sent) then the last status read IORed with 0x8000 will be
returned.