' Name        : SPIX.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : 40-pin 16F877, 877A or similar
' Hardware    : LAB-X1 Experimenter Board
' Oscillator  : 4MHz external crystal
' Keywords    : LCDOUT, SHIFTIN, SHIFTOUT
' Description : PICBASIC PRO program to read and write to SPI SEEPROMs
' Writes to the first 16 locations of an external serial EEPROM. Then
' reads first 16 locations back and send to LCD repeatedly Note: for 
' SEEPROMs with word-sized address.
'

' Define LOADER_USED to allow use of the boot loader.
' This will not affect normal program operation.
Define LOADER_USED 1

' Define LCD registers and bits
Define LCD_DREG  PORTD
Define LCD_DBIT  4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG  PORTE
Define LCD_EBIT  1

Include "modedefs.bas"

CS  Var PORTA.5  ' Chip select pin
SCK Var PORTC.3  ' Clock pin
SI  Var PORTC.4  ' Data in pin
SO  Var PORTC.5  ' Data out pin

addr Var Word    ' Address
B0   Var Byte    ' Data

   TRISA.5 = 0   ' Set CS to output
   ADCON1 = 7    ' Set PORTA and PORTE to digital
   Low PORTE.2   ' LCD R/W line low (W)
   Pause 100     ' Wait for LCD to start up

   For addr = 0 To 15  ' Loop 16 times
     B0 = addr + 100   ' B0 is data for SEEPROM
     Gosub eewrite     ' Write to SEEPROM
     Pause 10          ' Delay 10ms after each write
   Next addr

mainloop:
   For addr = 0 To 15  ' Loop 16 times
     Gosub eeread      ' Read from SEEPROM
     Lcdout $fe,1,#addr,": ",#B0 ' Display
     Pause 1000
   Next addr
   Goto mainloop

' Subroutine to read data from addr in serial EEPROM
eeread:
   CS = 0              ' Enable serial EEPROM
   Shiftout SI, SCK, MSBFIRST, [$03, addr.byte1, addr.byte0] ' Send read command and address
   Shiftin SO, SCK, MSBPRE, [B0] ' Read data
   CS = 1              ' Disable
   Return

' Subroutine to write data at addr in serial EEPROM
eewrite:
   CS = 0               ' Enable serial EEPROM
   Shiftout SI, SCK, MSBFIRST, [$06] ' Send write enable command
   CS = 1               ' Disable to execute command
   CS = 0               ' Enable
   Shiftout SI, SCK, MSBFIRST, [$02, addr.byte1, addr.byte0, B0] ' Send address and data
   CS = 1               ' Disable
   Return

   End