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<h1>sramsw.c</h1><a href="sramsw_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment">00001 <span class="comment">/*! \file sramsw.c \brief Software-driven SRAM memory bus access functions. */</span>
00002 <span class="comment">//*****************************************************************************</span>
00003 <span class="comment">//</span>
00004 <span class="comment">// File Name : 'sramsw.c'</span>
00005 <span class="comment">// Title : Software-driven SRAM memory bus access functions</span>
00006 <span class="comment">// Author : Pascal Stang - Copyright (C) 2002</span>
00007 <span class="comment">// Created : 11/11/2002</span>
00008 <span class="comment">// Revised : 11/13/2002</span>
00009 <span class="comment">// Version : 1.0</span>
00010 <span class="comment">// Target MCU : Atmel AVR series</span>
00011 <span class="comment">// Editor Tabs : 4</span>
00012 <span class="comment">//</span>
00013 <span class="comment">// This code is distributed under the GNU Public License</span>
00014 <span class="comment">// which can be found at http://www.gnu.org/licenses/gpl.txt</span>
00015 <span class="comment">//</span>
00016 <span class="comment">//*****************************************************************************</span>
00017
00018 <span class="preprocessor">#include <avr/io.h></span>
00019 <span class="preprocessor">#include <avr/interrupt.h></span>
00020
00021 <span class="preprocessor">#include "<a class="code" href="global_8h.html">global.h</a>"</span>
00022 <span class="preprocessor">#include "<a class="code" href="sramsw_8h.html">sramsw.h</a>"</span>
00023
00024 <span class="comment">// global variables</span>
00025
00026 <span class="comment">// functions</span>
<a name="l00027"></a><a class="code" href="sramsw_8h.html#a0">00027</a> <span class="keywordtype">void</span> <a class="code" href="sramsw_8c.html#a0">sramswInit</a>(<span class="keywordtype">void</span>)
00028 {
00029 <span class="comment">// initialize port state</span>
00030 outb(SRAM_ADL, 0xFF); <span class="comment">// addr/data port set to 0xFF (pull-ups enabled)</span>
00031 outb(SRAM_AH, 0x00); <span class="comment">// high addr port set to 0x00</span>
00032 <span class="comment">// initialize port directions</span>
00033 outb(SRAM_ADL_DDR, 0x00); <span class="comment">// addr/data port set to input</span>
00034 outb(SRAM_AH_DDR, 0xFF); <span class="comment">// high addr port set to output</span>
00035 <span class="comment">// initialize control line states</span>
00036 sbi(SRAM_CTRL, SRAM_WR); <span class="comment">// de-assert write (active low)</span>
00037 sbi(SRAM_CTRL, SRAM_RD); <span class="comment">// de-assert read (active low)</span>
00038 cbi(SRAM_CTRL, SRAM_ALE); <span class="comment">// de-assert ALE (active high)</span>
00039 <span class="comment">// set control line direction</span>
00040 sbi(SRAM_CTRL_DDR, SRAM_WR);
00041 sbi(SRAM_CTRL_DDR, SRAM_RD);
00042 sbi(SRAM_CTRL_DDR, SRAM_ALE);
00043 <span class="comment">// set page lines direction</span>
00044 outb(SRAM_PAGE_DDR, inb(SRAM_PAGE_DDR) | SRAM_PAGE_MASK );
00045 <span class="comment">// initialize page</span>
00046 <a class="code" href="sramsw_8c.html#a4">sramswSetPage</a>(0);
00047 }
00048
00049 <span class="keywordtype">void</span> sramswOff(<span class="keywordtype">void</span>)
00050 {
00051 }
00052
<a name="l00053"></a><a class="code" href="sramsw_8h.html#a1">00053</a> <span class="keywordtype">void</span> <a class="code" href="sramsw_8c.html#a2">sramswWrite</a>(u32 addr, u08 data)
00054 {
00055 <span class="comment">// set page</span>
00056 <a class="code" href="sramsw_8c.html#a4">sramswSetPage</a>( (addr & 0x00FF0000)>>16 );
00057 <span class="comment">// set high-order address</span>
00058 outb(SRAM_AH, (addr & 0x0000FF00)>>8 );
00059 <span class="comment">// set low-order address</span>
00060 outb(SRAM_ADL, addr & 0x000000FF);
00061 <span class="comment">// apply low-order address to latch</span>
00062 outb(SRAM_ADL_DDR, 0xFF);
00063 <span class="comment">// clock latch to save low-order address</span>
00064 sbi(SRAM_CTRL, SRAM_ALE); <span class="comment">// assert ALE (active high)</span>
00065 <span class="keyword">asm</span> <span class="keyword">volatile</span> (<span class="stringliteral">"nop"</span>);
00066 cbi(SRAM_CTRL, SRAM_ALE); <span class="comment">// de-assert ALE (active high)</span>
00067
00068 <span class="comment">// apply data to memory</span>
00069 outb(SRAM_ADL, data);
00070 <span class="comment">// clock write line to store data</span>
00071 cbi(SRAM_CTRL, SRAM_WR); <span class="comment">// assert write (active low)</span>
00072 <span class="keyword">asm</span> <span class="keyword">volatile</span> (<span class="stringliteral">"nop"</span>);
00073 sbi(SRAM_CTRL, SRAM_WR); <span class="comment">// de-assert write (active low)</span>
00074 }
00075
<a name="l00076"></a><a class="code" href="sramsw_8h.html#a2">00076</a> u08 <a class="code" href="sramsw_8c.html#a3">sramswRead</a>(u32 addr)
00077 {
00078 u08 data;
00079
00080 <span class="comment">// set page</span>
00081 <a class="code" href="sramsw_8c.html#a4">sramswSetPage</a>( (addr & 0x00FF0000)>>16 );
00082 <span class="comment">// set high-order address</span>
00083 outb(SRAM_AH, (addr & 0x0000FF00)>>8 );
00084 <span class="comment">// set low-order address</span>
00085 outb(SRAM_ADL, addr & 0x000000FF);
00086 <span class="comment">// apply low-order address to latch</span>
00087 outb(SRAM_ADL_DDR, 0xFF);
00088 <span class="comment">// clock latch to save low-order address</span>
00089 sbi(SRAM_CTRL, SRAM_ALE); <span class="comment">// assert ALE (active high)</span>
00090 <span class="keyword">asm</span> <span class="keyword">volatile</span> (<span class="stringliteral">"nop"</span>);
00091 cbi(SRAM_CTRL, SRAM_ALE); <span class="comment">// de-assert ALE (active high)</span>
00092
00093 <span class="comment">// switch data bus to input</span>
00094 outb(SRAM_ADL_DDR, 0x00);
00095 <span class="comment">// clear pullups</span>
00096 outb(SRAM_ADL, 0x00);
00097 <span class="comment">// request data from memory</span>
00098 cbi(SRAM_CTRL, SRAM_RD); <span class="comment">// assert read (active low)</span>
00099 <span class="comment">// retrieve data</span>
00100 <span class="keyword">asm</span> <span class="keyword">volatile</span> (<span class="stringliteral">"nop"</span>);
00101 data = inb(SRAM_ADL_IN);
00102 <span class="comment">// release read line</span>
00103 sbi(SRAM_CTRL, SRAM_RD); <span class="comment">// de-assert read (active low)</span>
00104 <span class="comment">// switch data bus to output</span>
00105 outb(SRAM_ADL_DDR, 0xFF);
00106
00107 <span class="keywordflow">return</span> data;
00108 }
00109
<a name="l00110"></a><a class="code" href="sramsw_8h.html#a3">00110</a> <span class="keywordtype">void</span> <a class="code" href="sramsw_8c.html#a4">sramswSetPage</a>(u08 page)
00111 {
00112 outb(SRAM_PAGE, (page & SRAM_PAGE_MASK));
00113 }
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