Diff: Ser23K256.cpp

Revision:

2:f96c3c85aa3b

Child:

3:d2314b1ac797

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ser23K256.cpp	Sun Aug 15 13:06:52 2010 +0000
@@ -0,0 +1,91 @@
+// Ser23K256 - drive the Microchip 23K256 SRAM using SPI
+// Copyright (c) 2010 Romilly Cocking
+// Released under the MIT License: http://mbed.org/license/mit
+
+// 23K256 data sheet at http://ww1.microchip.com/downloads/en/DeviceDoc/22100B.pdf
+
+// Page-mode commands have not been implemented; I have found no need for them yet.
+
+// Assumes spi mode is default (8,0).
+
+// You can clock the 23K256 at up to 20MHz, so it supports the mbed's maximum SPI frequency of 12MHz.
+
+#include "mbed.h"
+#include "Ser23K256.h"
+
+Ser23K256::Ser23K256(SPI& spi, PinName ncs) : _spi(spi), _ncs(ncs)  {
+    deselect();
+}
+
+void Ser23K256::select() {
+    _ncs = 0;
+}
+
+void Ser23K256::deselect() {
+    _ncs = 1;
+}
+
+void Ser23K256::writeStatus(char status) {
+    select();
+    _spi.write(WRITE_STATUS);
+    _spi.write(status);
+    deselect();
+}
+
+char Ser23K256::readStatus() {
+    select();
+    _spi.write(READ_STATUS);
+    char result = (char) _spi.write(0);
+    deselect();
+    return result;
+}
+
+void Ser23K256::prepareCommand(char command, int address) {
+    select();
+    _spi.write(command);
+    _spi.write(address >> 8);
+    _spi.write(address & 0xFF);
+}
+
+// write or read a single byte
+
+void Ser23K256::write(int address, char byte) {
+    prepareCommand(WRITE, address);
+    _spi.write(byte);
+    deselect();
+}
+
+char Ser23K256::read(int address) {
+    prepareCommand(READ, address);
+    int result = _spi.write(0);
+    deselect();
+    return (char) result;
+}
+
+// buffered write and read
+
+/*
+* the single-byte read and write assume the 23K256 is in its default byte-mode
+* so sequential-model commands must switch the chip into sequential mode
+* at the start and return it to byte mode at the end.
+*/
+
+void Ser23K256::write(int address, char * buffer, int count) {
+    writeStatus(SEQUENTIAL_MODE);
+    prepareCommand(WRITE, address);
+    for (int i = 0; i < count; i++) {
+        _spi.write(buffer[i]);
+    }
+    deselect();
+    writeStatus(BYTE_MODE);
+}
+
+void Ser23K256::read(int address, char * buffer, int count) {
+    writeStatus(SEQUENTIAL_MODE);
+    prepareCommand(READ, address);
+    for (int i = 0; i < count; i++) {
+        buffer[i] = _spi.write(0);
+    }
+    deselect();
+    writeStatus(BYTE_MODE);
+}
\ No newline at end of file