GCBASIC documentation
SRAM ( Device )

Introduction:

Serial SRAM is a standalone volatile memory that provides an easy and inexpensive way to add more RAM to an application.  These are 8-pin, low-power devices.   They are high-performance devices with unlimited endurance and zero write times, making them ideal for applications involving continuous data transfer, buffering, data logging, audio, video, internet, graphics, and other math- and data-intensive functions.  

These devices are available from 64 Kbit up to 1 Mbit in density and support SPI, SDI, and SQI™ bus modes.  

The GCBASIC library only supports SPI bus mode.   The GCBASIC library supports hardware and software SPI — this is controlled via a constant, see below.

To use the SRAM library, simply include the following in your user code.  

This initialises the driver.  

    #define SPISRAM_CS      Porta.2      'Also known as SS, or Slave Select
    #define SPISRAM_SCK     Portc.3      'Also known as CLK
    #define SPISRAM_DO      Portc.5      'Also known as MOSI
    #define SPISRAM_DI      Portc.4      'Also known as MISO

    #define SPISRAM_HARDWARESPI
    #define SPISRAM_TYPE     SRAM_23LC1024

SRAM memory operations.   

The library exposes a set of methods to support use of SRAM memory.

The library requires a set of constants to support use of SRAM memory.

The library also exposes a constant that is specific to the device.   

This may be useful in the user program.   

This constant is used by the library.   

A user may use this public constant.

See Also:

Examples

    #include <uno_mega328p.h>
    #option explicit

   ' USART settings
    #define USART_BAUD_RATE 57600
    #define USART_DELAY 0 ms
    #define USART_BLOCKING
    #define USART_TX_BLOCKING


    'SD card attached to SPI bus as follows:
    '
    'UNO:    MOSI - pin 11, MISO - pin 12, CLK - pin 13, CS - pin 4 (CS pin can be changed) and pin #10 (SS) must be an output
    'Mega:   MOSI - pin 51, MISO - pin 50, CLK - pin 52, CS - pin 4 (CS pin can be changed) and pin #52 (SS) must be an output
    'Leonardo: Connect to hardware SPI via the ICSP header

    #define SPISRAM_CS      DIGITAL_5     'Also known as SS, or Slave Select
    #define SPISRAM_SCK      DIGITAL_13    'Also known as CLK
    #define SPISRAM_DO      DIGITAL_11    'Also known as MOSI
    #define SPISRAM_DI      DIGITAL_12    'Also known as MISO

    #define SPISRAM_HARDWARESPI
    #define SPISRAM_TYPE     SRAM_23LC1024

    #define HWSPIMode MASTERULTRAFAST       'MASTERSLOW | MASTER | MASTERFAST | MASTERULTRAFAST for specific AVRs only. Defaults to MASTERFAST


  '********************************************************************************

  'Main program

    'Wait 2 seconds to open the serial terminal
    wait 2 s

    HSerPrintCRLF 2
    HSerPrint "Writing..."
    HSerPrintCRLF
    For SRAM_location=0 to SPISRAM_CAPACITY - 1
     SRAMWrite ( [long]SRAM_location, SRAM_location and 255 )          ' <<< the SRAMWrite instruction
    Next


    dim spirambyteread as Byte
    spirambyteread = 11
    HSerPrintCRLF 2
    dim SRAM_location as long
    HSerPrint "Reading..."
    HSerPrintCRLF
    For SRAM_location=0 to SPISRAM_CAPACITY - 1
     'choose one....
     'SRAMread ( SRAM_location, spirambyteread )
    'or, as a function
     spirambyteread = SRAMread ( SRAM_location )

     if spirambyteread = ( SRAM_location and 255 ) then
       HSerPrint hex(spirambyteread)
     else
       HSerPrint "**"
     end if
     HSerPrint ":"
    Next
    HSerPrintCRLF
    HSerPrint "Wait..."
    HSerPrintCRLF
    Wait 2 s

    HSerPrint "Rewriting to 0x00 ..."
    HSerPrintCRLF
    For SRAM_location=0 to SPISRAM_CAPACITY - 1
     SRAMWrite ( [long]SRAM_location, 0 )
    Next

    Dim errorcount as long
    errorcount = 0
    For SRAM_location=0 to SPISRAM_CAPACITY - 1
     SRAMRead ( SRAM_location, spirambyteread )
     if spirambyteread <> 0 then
       errorcount++
     end if
    Next
    HSerPrint "Error Count (should be 0) = "
    HSerPrint errorcount
    HSerPrintCRLF
    HSerPrint "End..."
    HSerPrintCRLF
    end

Key line: SRAMWrite ( [long]SRAM_location, SRAM_location and 255 ) — writes one test pattern byte to every address the attached SRAM chip supports, verified by the read-back loop further down.