I2C with 16F628A mystery

[lilimike]

Thank you Peter,

I understand the first part of your response but not sure about the second part:

Now the PBP manual states "The Address size sent (byte or word) is determined by the size of the variable that is used. If a byte-sized variable is used for the Address, an 8-bit address is sent. If a word-sized variable is used, a 16-bit address is sent. Be sure to use the proper sized variable for the device you wish to communicate with."

I suspect this is in fact not correct and looking at the assembler code that PBP generates, in fact I2CWRITE seems to send a word, using I2CAddr, I2CAddr2 as the (word) address in my example, or the case of your code, actually I2CAddr, I2CDevice (=$A0) which is I suspect somewhere other than you intended in memory!

I will continue to read it over and over, some times it takes me a few times to understand.

Now again I am running into some mystery and I wish I could understand better...

If I run this code:

i2cdevice =$A0
for i2caddr = 0 to 2048 step 16
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$ff]:pause 10
next

Then I read the EPROM with Ponyprog and observed everything as expected.


Then I rewrote my code by changing:

for i2caddr = 0 to 2048 step 16

to

for i2caddr = 0 to 1024 step 16

and the 3 first line I replaced $01 by $ff.

I was expecting to see half of the memory filled with my changes but it got filled all the way to address $7FF:


The more I test the more I get confused!

Mike