3. I2C Address and Start Sending Routine

baseaddr% = &h310 ‘* adapter’s base address = 0x310 (hex) * controladdress% = baseaddr% + 1

status% = FNgetstatus%(controladdress%)

print”I2C Communications Adapter Status = “;status%

‘* This will read the I2C Communications Adapter’s current status *

5.2.3.I2C Address and Start Sending Routine

Name:	sendaddress(baseaddr%, slv%, setnack%)
Usage:	call sendaddress(baseaddr%, slv%, setnack%)
Function:	procedure to send Start and slave address of device that is to be communicated
	with.
Parameters are:
baseaddr%	the base address of the I2C Communications Adapter set by links on circuit
	board.
slv%	the 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.
setnack%	this controls whether the 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, in all other cases acknowledge
	must be enabled. If setnack% = 0 then acknowledge must be 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 to =
	1; in all other cases it must be set = 0.
Value Returned:none.

I2C Status on exit from routine:

	The status of the I2C Communications Adapter will be either &h00 - bus busy and
	unread data in data register or &h80 - bus busy and no unread data in data
	register when a Start and Slave Address have been successfully transmitted (see
	Appendix A for details of status codes).
Example Usage:	(see also sample programs)
$include “i2c.inc”	‘* This contains the I2C routines*
baseaddr% = &h310	‘* Adapter’s base address = 0x310 (hex) *
slv% = &ha0	‘* IC Address of slave, this is a typical write *
	‘* address for an I2C static RAM or EEPROM *
setnack% = 0	‘* Enable Acknowledge (see parameter descriptions) *

call sendaddress (baseaddr%, slv%, setnack%) print”Start and I2C Slave Address sent”

‘* This will send a Start and the I2C Slave Address of the device to be communicated with. *

Name:	FNreadbyte%(baseaddr%, setnack%)
Usage:	databyte% = FNreadbyte%(baseaddr%, setnack%)
Function:	function to read a byte of data from a slave device whose slave address has
	already been sent by sendaddress. Can be used to disable acknowledge after
	reading data if it is the last but one byte to be read.
Parameters are:
baseaddr%	the base address of the I2C Communications Adapter set by	links on circuit
	board.

Revision 1.7	Page 12 of 27
09/12/1999