In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Mike_W wrote:

[2]
I am using A 24C02 EEPROM with a SX28 

the A2,A1,A0 pins are hard wired to VCC

I used the I2C help and examples to come up with this code. and all is fine, I can write and read to and from the EEPROM.

My example writes the value 25 to memory locarion 256. and then reades it back

( I am also using a LCD display but omitted that code to make the post shorter)

My question is?

When I write to the EEPROM I have to use an Address (Addr) of 256 or larger. WHY? Is this because I have A2,A1,A0 hard wired to VCC or have I done something else wrong and missed it

Thanks

Mike

 

 

' -------------------------------------------------------------------------

DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX

FREQ 4_000_000

' -------------------------------------------------------------------------

' IO Pins

' -------------------------------------------------------------------------

Serial_Data PIN RA.0 INPUT ' SDA

Serial_Clock PIN RA.1 INPUT ' SCL

' -------------------------------------------------------------------------

' Constants

' -------------------------------------------------------------------------

SlaveID CON %10101110 ' for 24C02 A0,A1,A2 hard wired high (174 $AE)

Ack CON 0 ' Control Protocol to acknowledge receipt 

Nak CON 1 ' negative acknowledgment or not acknowledged

Addr CON $100 ' Word Address in 24C02 256 or larger

' -------------------------------------------------------------------------

' Variables

' -------------------------------------------------------------------------

flags VAR Byte ' flag for read or write eight bit

ackVal VAR flags.0 ' ackVal bit.0, (0 = write 1 = read)

tmpB1 VAR BYTE ' work vars

tmpB2 VAR BYTE '

tmpB3 VAR BYTE '

tmpW1 VAR WORD '

' =========================================================================

PROGRAM Start

' =========================================================================

' -------------------------------------------------------------------------

' Subroutine Declarations

' -------------------------------------------------------------------------

DEVICE_WRITE SUB 3 ' write value to memory

DEVICE_READ FUNC 1, 2 ' read byte from memory

I2C_IN FUNC 1, 1 ' read byte from Serial_Data

I2C_START SUB 0 ' generate I2C Start

I2C_STOP SUB 0 ' generate I2C Stop

I2C_OUT SUB 1, 1 ' write byte to Serial_Data

' -------------------------------------------------------------------------

' Program Code

' -------------------------------------------------------------------------

Start:

Main:

tmpB2 = 25

Device_Write Addr, tmpB2 write 25 to address 256

(more code Here)

tmpB2 = Device_Read Addr ' read from 24C02

 

END 

' -------------------------------------------------------------------------

' Subroutines Code

' -------------------------------------------------------------------------

' -------------------------------------------------------------------------

SUB DEVICE_WRITE

tmpW1 = __WPARAM12 ' copy Address

tmpB1 = __PARAM3 ' copy value

I2C_START

tmpW1_MSB = tmpW1_MSB & $03 ' get block value

tmpW1_MSB = tmpW1_MSB << 1

tmpW1_MSB = tmpW1_MSB | SlaveID ' create control byte

tmpW1_MSB.0 = 0 ' set RW bit for write

I2C_OUT tmpW1_MSB ' send slave ID

I2C_OUT tmpW1_LSB ' send word Address

I2C_OUT tmpB1 ' send data byte

I2C_STOP ' finish

DO ' let write cycle finish

I2C_START

I2C_OUT tmpW1_MSB ' resend slave ID

LOOP UNTIL ackVal = Ack

ENDSUB

' -------------------------------------------------------------------------

FUNC DEVICE_READ

tmpW1 = __WPARAM12 ' copy Address

I2C_START

tmpW1_MSB = tmpW1_MSB & $03 ' get block value

tmpW1_MSB = tmpW1_MSB << 1

tmpW1_MSB = tmpW1_MSB | SlaveID ' create control byte

tmpW1_MSB.0 = 0 ' set RW bit for write

I2C_OUT tmpW1_MSB ' send slave ID

I2C_OUT tmpW1_LSB ' send word Address

I2C_START ' restart for read

tmpW1_MSB.0 = 1 ' set RW bit for Read

I2C_OUT tmpW1_MSB '

tmpB1 = I2C_IN Nak '

I2C_STOP '

RETURN tmpB1

ENDFUNC

' -------------------------------------------------------------------------

SUB I2C_START '

I2CSTART Serial_Data '

ENDSUB

' -------------------------------------------------------------------------

SUB I2C_STOP '

I2CSTOP Serial_Data ' 

ENDSUB

' -------------------------------------------------------------------------

SUB I2C_OUT '

I2CSEND Serial_Data, __PARAM1, ackVal '

ENDSUB

' -------------------------------------------------------------------------

FUNC I2C_IN '

ackVal = __PARAM1.0 '

I2CRECV Serial_Data, tmpB3, ackVal '

RETURN tmpB3 '

ENDFUNC

' -------------------------------------------------------------------------
[/2]

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