CALIBRE
4.2.6.Send an I2C Stop Routine
Function definition: | int sendstop(void) |
Usage: | i2cstatus = sendstop(); |
Function: | This is the procedure to send a stop (end of communication signal) down the |
| I2C Bus, ending a transmission or reception with a slave which was |
| addressed previously by sendaddress. |
Parameters are: Value Returned:
I2C status on exit:
Example Usage:
None.
int i2cstatus.
The value returned depends on whether the bus became free. If the bus became free then the status (0x81) is returned.
If the bus does not became free then the last status read IORed with 0x8000 will be returned.
The function will read the status a number of times, waiting for the bus to become free, before returning an none free status - this number is defined by the MAXNUMBEROFGOES constant defined in I2CINC.C, this value may be altered to suit your system.
The status of the Parallel I2C Communications Adapter will be 0x81 - bus idle and no unread / untransmitted data in data register.
Note - this may not be the case in a system where there is another master as well as the Parallel I2C Communications Adapter, since this other master may well have taken control of the bus by the time a program next uses getstatus to read the status register.
(See Appendix A for details of status codes). (see also sample programs)
/* This will write a Stop to the I2C Bus */ main()
{
int i2cstatus;
i2cstatus = sendstop();
printf("Stop has been transmitted status is %x\n", i2cstatus);
}
4.2.7.I2C Restart and Address Sending Routine
Function Definition: | int restart(int slaveaddress, int setnack) |
Usage: | i2cstatus = restart(slaveaddress, setnack) |
Function: | This is the procedure to send Restart and slave address of device which is to |
| be communicated with, without a Stop having been sent at the end of last |
| transmission/reception. This routine is particularly useful for reading |
| memories which must first have a data pointer written to them to select where |
| the read is to occur from, and must have their address sent a Restart to |
| proceed with the read operation. |
Issue 1.3 | Page 12 |
22/07/99