hi all,
        I am a relatively new PIC user. I am using the PIC16F876 with a 4Mhz
Crystal. I was trying to get the MSSP module on the pic to communicate with a
I2C EEPROM (Atmel 24c16). I tried writing the program myself, but it did not
work. So i looked up the FAQs on this list, and came up with a program. I
modified it a little to suit my needs. It still refused to work. I isolated
the error to the point where I set up SEN in SSPCON2. I have attached the
relevant parts of the program.

        103 start_i2c MACRO              ;[S]
        104      Bank0
        105      movlw 's'
        106      movwf TXREG
        107      call Dlay
        108      bcf PIR1,SSPIF
        109      Bank1                                           ;bank1
        110      bsf SSPCON2,SEN        ;send i2c START [S] bit
        111      Bank0                                       ;bank0
        112      movlw ','
        113      movwf TXREG
        114      call Dlay
        115      movlw ','
        116      movwf TXREG
        117      btfss PIR1,SSPIF         ;start bit cycle complete?
        118      goto $-2
        119      movlw 'S'
        120      movwf TXREG
        121      call Dlay
        122      endm
        123
        124 enable_receive_i2c MACRO
        125      Bank1                                           ;bank1
        126      bsf SSPCON2,RCEN       ;enable receiving at master 16f876
        127      Bank0                                           ;bank0
        128      bcf PIR1,SSPIF
        129      btfss PIR1,SSPIF               ;sspbuf buffer full byte?
        130      goto $-1
        131      endm
        132
        133 stop_i2c MACRO                  ;[P]
        134      Bank0                                           ;bank0
        135      bcf PIR1,SSPIF
        136      Bank1                                           ;bank1
        137      bsf SSPCON2,PEN         ;send i2c STOP [P] bit
        138      Bank0                                           ;bank0
        139      btfss PIR1,SSPIF               ;stop bit cycle completed?
        140      goto $-1
        141      endm
        142
        143 wait_for_ack_i2c MACRO
        144      Bank0                                           ;bank0
        145      movlw 'w'
        146      movwf TXREG
        147      call Dlay
        148      bcf PIR1,SSPIF
        149      btfss PIR1,SSPIF                 ;ACK received?
        150      goto $-1
        151      movlw 'W'
        152      movwf TXREG
        153      call Dlay
        154      endm
        155
        156 setup_i2c MACRO                          ;setup mssp for i2c
        157      movlw '+'
        158      movwf TXREG
        159      call Dlay
        160      movlw 0x28
        161      movwf SSPCON
        162      Bank1
        163      movlw 0x80
        164      movwf SSPSTAT
        165      movlw 0x60
        166      movwf SSPCON2
        167      movlw 9
        168      movwf SSPADD
        169      Bank0
        170      movlw '*'
        171      movwf TXREG
        172      call Dlay
        173      endm
        174
        175 read_mem     MACRO
        176       start_i2c
        177       movlw 0xA1
        178       movwf SSPBUF
        179       wait_for_ack_i2c
        180       enable_receive_i2c
        181       movf SSPBUF,W
        182       movwf mem_rd_data
        183       stop_i2c
        184       endm
        185
        186 write_mem MACRO
        187       start_i2c
        188       movlw 0xA0
        189       movwf SSPBUF
        190       wait_for_ack_i2c
        191       movf mem_wr_data,W
        192       movwf SSPBUF
        193       wait_for_ack_i2c
        194       stop_i2c
        195       endm
        196
        197 loop
        198       setup_i2c
        199 loop2
        200       movlw 'a'
        201       movwf TXREG
        202       call Dlay
        203       movwf mem_wr_data
        204       write_mem
        205       movlw '-'
        206       movwf TXREG
        207       call Dlay
        208       read_mem
        209       movf mem_rd_data,W
        210       movwf TXREG
        211       call Dlay
        212       goto loop2

        the error occurs when we set the SSPCON2,SEN and then wait for SSPIF to be
set. The flag is never set, and the program goes into an infinte loop. Please
see lines numbered 117,118. The USART communications are for me to know what
th pic is doing currently and do not have any other pupose as such. I just
can't make out where i am going wrong. I would be thankful to anyone who
could suggest corrections to the above code, or maybe give me a better way to
use the MSSP.

Thanking all in advance.
--
Sirish.K.A
DeepRoot Linux Pvt. Ltd.
Yelahanka
Bangalore -560064
Ph : +91(80)8565624

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