Good afternoon Ken,

Yup, thank for reminding me that. I saw my mistake already.

Fosc = 40MHz
Baud rate = 400KHz

Therefore, SSPADD = (Fosc/4*Baud rate)-1

In the case I will get, SSPADD = 24;    //400KHZ Baud clock @ 40MHz

Am I correct to say that?

I have rewrite the I2C_inital as shown below. I added in the SSPCON1 which I
miss out at first. But I do not know whether the C18 complier command
OPENI2C(MASTER, SLEW_ON) is the same as using SSPCON1.

Just for you to verify.

//I2C_init condition
TRISC = 0X18;                               //Set SDA (PIN 4) & SCL (PIN3)
as input. Activate I2C port
OpenI2C(MASTER, SLEW_ON);  //Initialize I2C module
SSPADD = 24;                                //400KHz Baud clock @ 40MHz
SSPCON1 = 0x28;                          //set up SCL & SDA as the source
for the serial port and set the I2C module to master mode

Thank you,
Nicholas

----- Original Message -----
From: "Ken Pergola" <no_spam@LOCALNET.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, March 20, 2004 4:30 PM
Subject: Re: [PIC]:I2C DAC test


> Nicholas,
>
> Now that I know you are using a 40 MHz clock for the PIC18F452 you must
> change the value you are loading into SSPADD:
>
> You are loading a value of 0x09, but if your Fosc to the PIC is 40 MHz,
then
> your SCL clock frequency is actually 1 MHz!
> Clearly this is in violation of the MAX417 (which is rated at 400 KHz
> maximum). I'm not saying this will fix your problem, but you don't want to
> operate above the manufacturer's specifications.
>
> In other words Nicholas this line of code would be wrong for an external
> clock of 40 MHz:
>
>     SSPADD = 9;     //400KHz Baud clock (9) @16MHz
>
>
> Your homework assignment:
>
> Calculate a new SSPADD value, report back and I will verify the value you
> calculated.
>
>
> Best regards,
>
> Ken Pergola
>
> --
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