Function: | procedure to send a Stop (end of communication signal) down the I2C Bus, |
| ending a transmission or reception with a slave that was address previously by |
| sendaddress. |
Parameters are: |
|
controladdress% | The address of the I2C Communications Adapter control register, equal to |
| 1+(base address set by links on circuit board). |
Value Returned:none. |
|
I2C status on exit from routine:
The status of the I2C/ 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 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).
Example Usage: $include “i2c.inc” baseaddr% = &h310 controladdress% = baseaddr% + 1 call sendstop(controladdress%) print”Stop has been transmitted”
‘* This will write a stop to the I2C Bus*
(see also sample programs)
‘* This contains the I2C routines*
‘* Adapter’s base address = 310 (hex) * ‘* Control Register address *
5.2.7.I2C 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 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 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 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. |
|
I2C status on exit from routine:
| The status of the I2C/ 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 I2C routines* |
|
baseaddr% = &h310 | ‘* Adapter’s base address = 310 (hex) * | |
Revision 1.7 |
| Page 14 of 27 |
09/12/1999 |
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