' Name        : EEPAGEX.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : 40-pin 16F877A
' Hardware    : LAB-X1 Experimenter Board
' Oscillator  : 4MHz external crystal
' Keywords    : HSEROUT, I2CREAD, I2CWRITE, I2C EEPROM
' Description : PICBASIC PRO to demonstrate the page-write
' capability of the 24LC256 serial memory. This program will
' transfer 64 bytes of data to the memory before a pause is
' needed to complete the write.
'

' Set receive register to receiver enabled
Define HSER_RCSTA 90h

' Set transmit register to transmitter enabled
Define HSER_TXSTA 24h

' Set baud rate
Define HSER_BAUD  9600

scl  VAR PORTC.3        ' Clock pin
sda  VAR PORTC.4        ' Data pin
addr VAR WORD           ' Memory Address
i    VAR BYTE           ' Loop counter

data_array VAR BYTE[64] ' Data array with location for checksum

   ADCON1 = 7           ' Set PORTA and PORTE to digital
        
   HSerout ["Programming", 10,13]

   For i = 0 to 63      ' Load the array with test data
      data_array[i] = i
   Next i

' From the Microchip memory databook:  
' Page write operations are limited to writing bytes within a single
' physical page, regardless of the number of bytes actually being written.

' Physical page boundaries start at addresses that are integer multiples
' of the page buffer size (or 'page size') and end at addresses that are
' integer multiples of [page size - 1].

' If a Page Write command attempts to write across a physical page boundary,
' the result is that the data wraps around to the beginning of the current
' page (overwriting) data previously stored there), instead of being written
' to the next page, as might be expected. It is, therefore, necessary for the
' application software to prevent page write operations that would attempt to
' cross a "page boundary."

   For addr = 0 To 32767 Step 64   ' Store $00 to all locations (for testing)
      I2CWrite sda,scl,$A0,addr,[STR data_array\64]  ' Send a 64-byte page
       HSerout ["."]               ' Indicate progress           
       Pause 10                    ' Pause 10mS to let the write complete
   Next addr

' Spot-check the data on the terminal screen
   i = 0
   Hserout [10,13, 10,13, "checking", 10,13]

   For addr = 0 to 32767 Step 257       ' read every 257th address
      i = i + 1
      I2CRead sda, scl, $A0, addr, [data_array[0]] ' Read a single byte from memory
      Hserout [HEX2 data_array[0], " "] ' To terminal with hex value 
      If (i & $0007) = 0 Then           ' Break it into organized lines
         Hserout [10,13]                ' 8 locations to a line
      Endif
   Next addr                            ' Go get the next test

   End     ' Stop