Calibre UK IC Communication Adapter ICA93LV User Manual - page 15

Revision 1.7

Page 14 of 27

09/12/1999

Function:

procedure to send a Stop (end of communication signal) down the I

2

C Bus,

ending a transmission or reception with a slave that was address previously by

sendaddress.

Parameters are:

controladdress%

The address of the I

2

C Communications Adapter control register, equal to

1+(base address set by links on circuit board).

Value Returned:none.

I

2

C status on exit from routine:

The status of the I

2

C/ the Communications Adapter will be &h81 - bus idle and no

unread/untransmitted data in the data register. Note - this may not be the case in

a system where there is another master as well as the I

2

C 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).

Example Usage:

(see also sample programs)

$include “i2c.inc”

‘* This contains the I

2

C routines*

baseaddr% = &h310

‘* Adapter’s base address = 310 (hex) *

controladdress% = baseaddr% + 1

‘* Control Register address *

call sendstop(controladdress%)

print”Stop has been transmitted”

‘* This will write a stop to the I

2

C Bus*

5.2.7.

I

2

C Restart and Address Sending Routine

Name:

restart(baseaddr%, slv% setnack%)

Usage:

call restart(baseaddr%, slv%, setnack%)

Function:

procedure to send a Restart and the slave address of device that is to be

communicated with, without a Stop having been sent at the end of the 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 then have their read address sent with a Restart to

proceed with the read operation.

Parameters are:

baseaddr%

the base address of the I

2

C 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 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 I

2

C Communications Adapter transmits an

Acknowledge down the I

2

C 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 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.

I

2

C status on exit from routine:

The status of the I

2

C/ the Communications Adapter will be either &h00 - bus the

busy and unread data in the data register or &h80 - bus busy and no unread data

in the data register when a Restart and Salve Address have been successfully

transmitted (see Appendix 

A for details of Status Codes).

Example Usage:

$include “i2c.inc”

‘* This contains the I

2

C routines*

baseaddr% = &h310

‘* Adapter’s base address = 310 (hex) *