Appendix b – i, C communications adapter control codes – Calibre UK IC Communication Adapter ICA93LV User Manual
Page 25
Revision 1.7
Page 24 of 27
09/12/1999
Appendix B – I
2
C Communications Adapter Control Codes
The Control Register should normally be written using the setup, sendaddress and sendstop routines. To
implement more advanced functions such as enabling hardware interrupt generation or implementing
long distance mode, these routines may need to be modified or the users own routines used in their
place.
The Control Register is accessed by writing to I/O address:
1+Base address of card (set by links on board).
The Data Register is accessed by writing to I/O address:
Base address of card (set by links on board).
E.g. in C, outp(0x311, 0xc3); would cause an I
2
C Communications Adapter with base address = 0x310 to
generate a Stop condition on the I
2
C bus. For detailed information on these codes, the Philips data sheet
on the PCF8584 device (see Section 8, Further Information)
0x00
read/write own address register (followed by a data byte to the data register).
0x20
read/write clock register (followed by a data byte to the data register).
After either of the above operations, 0x41 must be written to the control register to re-enable the I
2
C
interface.
0xc3
send a Stop signal over the I
2
C bus.
0x41
I
2
C NOP (no operation) instruction, acknowledge enabled.
(Use 0x41 and 0x40 to turn on and off acknowledge)
0x45
(While bus is free) - Send Start & slave address, acknowledge enabled. The address to
be sent must have first been written to the data register before sending the startcode.
0x45
(While already master on the bus) - Send Repeated Start & slave address (Restart). The
address to be sent is placed in the data register after sending the start code.
0x47
send Stop, Start, slave address (i.e. restart transmission without releasing control of the
I
2
C bus). The address to be sent is placed in the data register after sending the start
code.
To execute the last four instructions with acknowledge disabled, i.e. negative acknowledge - nack, set;
send the control code-1, e.g. 0x40, 0x44, 0x46.