Calibre UK PICA93LV ユーザーズマニュアル
CALIBRE
Issue 1.3
Page 16
22/07/99
Sub Main
slaveaddress% = &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)
i2cstatus% = sendaddress (slaveaddress%, setnack%)
Select Case i2cstatus%
case &H00
print "Start and I2C Slave Address sent and acknowledged"
case &H08
print "Start and I2C Slave Address sent and not acknowledged"
case else
print "Start not sent status is " + Hex$( i2cstatus%)
End Select
End sub
4.3.4.
I2C Read Data Byte from Slave Routine
Function definition:
readbyte%(setnack as integer)
Usage:
i2cdata% = readbyte%(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.
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:
setnack%
This controls whether the Parallel I2C Communications Adapter transmits
and 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 is enabled,
if setnack% = 1 then acknowledge is disabled. Therefore, if the LAST BUT
ONE byte is to be read, setnack% should be set to =1; in all other cases it
must be clear = 0. (In the case of reading 1 byte only, acknowledge will have
been disabled by sendaddress and so should now be enabled again after
reading the data.)
and 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 is enabled,
if setnack% = 1 then acknowledge is disabled. Therefore, if the LAST BUT
ONE byte is to be read, setnack% should be set to =1; in all other cases it
must be clear = 0. (In the case of reading 1 byte only, acknowledge will have
been disabled by sendaddress and so should now be enabled again after
reading the data.)
Value Returned:
i2cdata%
The value returned depends on whether the data was read successfully.
If the data was read then the value is returned.
If the data cannot be read (because there is none in the register) then the last
status read IORed with &H8000 will be returned.
status read IORed with &H8000 will be returned.
The function will read the status a number of times before returning an error
condition - this number is defined by the MAXNUMBEROFGOES constant
defined in I2CINC.C, this value may be altered to suit your system.
condition - this number is defined by the MAXNUMBEROFGOES constant
defined in I2CINC.C, this value may be altered to suit your system.
I2C status on exit :
0x00 bus busy and unread data in data register.
0x80 bus busy and no unread data in data register
The value will depend on whether any more bytes of data have been
transmitted by the slave device which is being read.
transmitted by the slave device which is being read.