Q:What pins should be used when interfacing a PIC or SX to IIC devices? Would open-drain pin RA4 would be the pin to use for SDA on an PIC xF84 then to make life a little easier ?
A: from Ken Webster
Perhaps. I actually found the ordinary pins quite easy to use on a 16C74, particularly because it is ok to use BCF and BSF directly on the TRISA, TRISB, or TRISC registers (thus you needn't use a mirror register like you do with PORTA, PORTB, or PORTC with read-modify-write instructions).
For example, with an open-drain pin:BSF PORTA_MIRROR,2 MOVF PORTA_MIRROR,W MOVWF PORTA
With an ordinary pin:
Toggling a pin high:BSF STATUS,RP0 BSF TRISA,2 BCF STATUS,RP0
A shortcut I often used was to point FSR at TRISA at the start of a subroutine that talks to the EEPROM. Then, in the body of ths subroutine, I could use the following (instead of switching STATUS,RP0 back and forth):BSF INDF,2
So, actually, I think it is easier to not use an open-drain pin as long as you can use 2 pins on the same port and point FSR to that port. For the 17C756 I chose to use the open-drain pins only because they were not useful for anything else and I was short on pins.
|file: /Techref/io/i2c/odvspin.htm, 1KB, , updated: 2002/11/4 10:25, local time: 2018/7/22 08:11,
|©2018 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?|
<A HREF="http://www.piclist.com/techref/io/i2c/odvspin.htm"> io i2c odvspin</A>
|Did you find what you needed?|
We sell a few items to support this site
Welcome to www.piclist.com!