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<title>
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SSBCC -- PERIPHERAL
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</title>
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<body>
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<tt>Copyright 2012, Sinclair, R.F., Inc.</tt><br/>
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<h1>Table of Contents</h1>
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<a href="#introduction">Introduction</a><br/>
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<a href="#command">Command</a><br/>
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<a href="#cores">9x8 Cores</a><br/>
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<a href="#new">Creating new Peripherals</a><br/>
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<a href="#recommendations">Reccomendations</a><br/>
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<h1><a name="introduction">Introduction</a></h1>
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Within the processor configuration command, the PERIPHERAL configuration is used
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to incorporate peripherals such as UARTs, TBD into the micro controller
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core.<br/><br/>
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This document describes the general format of the peripheral configuration
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command, lists peripherals for the 9x8 core, and documents how to add
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additional peripherals to the computer compiler.<br/><br/>
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<h1><a name="command">Command</a></h1>
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TODO
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<h1><a name="cores">9x8 Cores</a></h1>
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TODO
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<h1><a name="new">Creating new Peripherals</a></h1>
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New peripherals are created using a Python class with the following member
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functions:
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<h2>__init__(self,config,param_list):</h2>
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Where:<br/>
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<ul>
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<li><tt>config</tt> is the computer compiler configuration state when
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the peripheral configuration command is encountered.<br/><br/></li>
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<li><tt>param_list</tt> is a list of the space separated parameters on
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the peripheral
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configuration command following the name of the peripheral. This list
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is used to provide mandatory and optional parameters to the
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core. For example, the <tt>UART_Tx</tt> peripheral requires
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information to generate the desired baud rate and allows an optional
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name to facilitate distinguishing between multiple instances of the
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same peripheral.<br/><br/>
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For example, the parameters in the peripheral configuration
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command<br/><br/>
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<tt> PERIPHERAL name param1 \<br/>
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param2=options \<br/>
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param3="a string" \<br/>
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param4=value</tt><br/><br/>
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is converted to the space delimited string<br/><br/>
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<tt> param1 param2=option param3="a string" param4=value</tt><br/><br/>
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which is then provided to the <tt>__init__</tt> function as a
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<tt>list()</tt> with the following four tuples:<br/><br/>
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<tt> ('param1',)<br/>
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('param2','option',)<br/>
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('param3','"a string"',)<br/>
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('param4','value',)</tt><br/><br/>
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These tuples can then be parsed within the <tt>__init__</tt> function to
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intialize the object.<br/>
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</li>
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</ul>
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This function should store instantiation specific information in
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<tt>self</tt>.<br/><br/>
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Inputs from the FPGA fabric to the micro controller module are added by
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appending a tuple describing the input. The tuple consists of the
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following:<br/>
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<ol>
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<li>signal name</li>
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<li>signal width</li>
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<li>signal type: the string <tt>'input'</tt><br/></li>
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</ol>
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For example, to add an 8-bit input named "<tt>i_new_input</tt>", use the
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following statement:<br/><br/>
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<tt> config['ios'].append(('i_new_input',8,'input',));</tt><br/><br/>
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Outputs from the micro controller to the FPGA fabric are added using the
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signal type <tt>'output'</tt>. For example, to add an 8-bit output
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named "<tt>o_new_output</tt>", use the following statement:<br/><br/>
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<tt> config['ios'].append(('o_new_output',8,'output',));</tt><br/><br/>
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Similarly, to add a 16-bit tri-state input/output signal, use the
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followiing statement:<br/><br/>
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<tt> config['ios'].append(('io_new_signal',16,'inout',));</tt><br/><br/>
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To add a signal or a composite signal output from the micro controller
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core to the peripheral two actions are required. These can be done in
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either order, but it may make more sense to maintainers or subsequent
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users to do them in the following order:<br/><br/>
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<ol>
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<li>Add the output port to the micro controller core:<br/><br/>
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This consists of adding a tuple to <tt>config['outports']</tt>. The
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first element of this tuple is the name of the outport. The
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subsequent elements of this tuple are tuples describing the
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signal(s) associated with the outport. These tuples have the
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following ordered format:<br/><br/>
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<ol>
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<li>signal name</li>
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<li>signal width</li>
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<li>signal type: <tt>'data'</tt> or <tt>'strobe'</tt><br/>
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Note: Signal type <tt>'data'</tt> is used to relay single or
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multiple bit data from the micro controller core to the
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peripheral. Signal type <tt>'strobe'</tt> generates a single
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bit strobe during the clock cycle immediately following the
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<tt>outport</tt> instruction.<br/><br/>
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</li>
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</ol>
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<li>Add these same signals to <tt>config['signals']</tt>, one at a
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time using tuples with the following ordered format:<br/><br/>
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<ol>
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<li>signal name</li>
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<li>signal width<br/></li>
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</ol>
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</li>
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</ol>
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For example, to add two outputs from the micro controller core to a
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multiplier, use the following:<br/><br/>
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<tt> config['outports'].append(('O_MULT_A',<br/>
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('s_mult_a',8,'data'),<br/>
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));<br/>
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config['outports'].append(('O_MULT_B',<br/>
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('s_mult_b',8,'data'),<br/>
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));<br/>
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config['signals'].append(('s_mult_a',8,));<br/>
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config['signals'].append(('s_mult_b',8,));</tt><br/><br/>
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As a second example, to add an output from the micro controller core
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to the input side of an 8-bit FIFO, use the following. Here, the signal
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<tt>s_fifo_data</tt> will be the data to write to the FIFO and
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<tt>s_fifo_wr</tt> will be a strobe that is set high during the clock
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cycle immediately following the <tt>outport</tt> instruction.<br/><br/>
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<tt> config['outports'].append(('O_FIFO',<br/>
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('s_fifo_data',8,'data'),<br/>
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('s_fifo_wr',1,'strobe'),<br/>
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));<br/>
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config['signals'].append(('s_fifo_data',8,));<br/>
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config['signals'].append(('s_fifo_wr',1,));</tt><br/><br/>
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Adding a signal or a composite signal from the peripheral to the micro
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controller core requires two similar actions:<br/>
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<ol>
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<li>Add the input port to the micro controller core:<br/><br/>
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This consists of adding a tuple to <tt>config['inports']</tt>. The
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first element of this tuple is the name of the inport. The
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subsequent elements of this tuple are tuples describing the
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signal(s) associated with the inport. These tuples have the
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following ordered format:<br/><br/>
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<ol>
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<li>signal name</li>
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<li>signal width</li>
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<li>signal type: <tt>'data'</tt>, <tt>'set-reset'</tt>, or
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<tt>'strobe'</tt>
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Note: Signal type <tt>'data'</tt> is used to relay single or
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multiple bit data from the peripheral to the micro controller
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core. Signal type <tt>'set-reset'</tt> latches the associated
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input bit until the signal is read, at which time it is cleared.
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Signal type <tt>'strobe'</tt> generates a single bit strobe
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during the clock cycle immediately following the
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<tt>inport</tt> instruction.<br/>
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Note: The <tt>'set-reset'</tt> signal type is provided as a
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signal type for the <tt>INPORT</tt> command and may not be as
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useful for peripherals since the peripheral can include the
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associated logic required for the latch.<br/><br/>
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</li>
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</ol>
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<li>Add these same signals to <tt>config['signals']</tt>, one at a
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time using tuples with the following ordered format:<br/><br/>
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<ol>
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<li>signal name</li>
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<li>signal width<br/></li>
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</ol>
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</li>
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</ol>
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For example, to add two inport ports for the MSB and LSB from an 8 by 8 multipler, use the
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following:<br/><br/>
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<tt> config['inports'].append(('I_MULT_MSB',<br/>
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('s_mult_msb',8,'data'),<br/>
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));<br/>
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config['inports'].append(('I_MULT_LSB',<br/>
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('s_mult_lsb',8,'data'),<br/>
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));<br/>
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config['signals'].append(('s_mult_msb',8,));<br/>
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config['signals'].append(('s_mult_lsb',8,));</tt><br/><br/>
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As a second example, to add an input port from a FIFO in the
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peripheral to the micro controlller core, use the following:<br/><br/>
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<tt> config['inports'].append(('I_FIFO',<br/>
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('s_fifo_data',8,'data'),<br/>
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('s_fifo_ack',1,'strobe'),<br/>
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));<br/>
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config['signals'].append(('s_fifo_data',8,));<br/>
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config['signals'].append(('s_fifo_ack',1,));</tt><br/><br/>
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As a third example, to add an input port for two status bits from a
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FIFO in the peripheral to the micro controlller core, use the
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following:<br/><br/>
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<tt> config['inports'].append(('I_FIFO_STATUS',<br/>
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('s_fifo_full',1,'data'),<br/>
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('s_fifo_empty',1,'data'),<br/>
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));<br/>
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config['signals'].append(('s_fifo_full',1,));<br/>
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config['signals'].append(('s_fifo_empty',1,));</tt><br/><br/>
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<h2>GenAssembly(self,config):</h2>
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This is an optional function to generate an assembly file associated with
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the peripheral.<br/>
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TODO
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<h2>GenHDL(self,fp,config):</h2>
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This function examines <tt>config['hdl']</tt> to determine the HDL language
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for generating the FPGA logic for the peripheral. The logic is written to
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the file handle <tt>fp</tt>.<br/><br/>
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Rather than capture all HDL languages in this function, the following type
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of structure is recommended:<br/><br/>
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<tt> GenHDL(self,fp,config):<br/>
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if config['hdl'] == 'Verilog':<br/>
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self.GenVerilog(fp,config);<br/>
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elif config['hdl'] == 'VHDL':<br/>
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self.GenVHDL(fp,config);<br/>
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else:<br/>
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raise Exception('HDL "%s" not implemented' % config['hdl']);</tt><br/><br/>
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For example, to generate the logic for an unsigned 8 by 8 multiplier using
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the previous inport, outport, and signal assignments, the Verilog code
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could be generated using:<br/><br/>
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<tt> GenVerilog(self,fp,config):<br/>
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fp.write('initial s_mult_msb = 8\'d0;\n');<br/>
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fp.write('initial s_mult_lsb = 8\'d0;\n');<br/>
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fp.write('always @ (posedge i_clk)\n');<br/>
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fp.write(' if (i_rst) begin\n');<br/>
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fp.write(' s_mult_msb <= 8\'d0;\n');<br/>
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fp.write(' s_mult_lsb <= 8\'d0;\n');<br/>
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fp.write(' end else\n');<br/>
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fp.write(' { s_mult_msb, s_mult_lsb } <= $unsigned(s_mult_a) * $unsigned(s_mult_b);\n');</tt><br/><br/>
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Note: The results of this multiplication are available two clock cycles
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after the <tt>outport</tt> instruction setting the <tt>s_mult_a</tt> or
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<tt>s_mult_b</tt> value. This isn't a problem with the processor as the
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<tt>outport</tt> is probably followed by a <tt>drop</tt>
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instruction and the <tt>inport</tt> instruction to read either part of the
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multiplication has to be preceded by an instruction pushing the port
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number onto the data stack.<br/><br/>
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Note: While Python allows the entire logic block to be written using a
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single <tt>fp.write("""initial s_...""");</tt> statement, breaking
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out the individual statements allows computed signal names to be included
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more cleanly and also accomodates conditional inclusion of code.<br/><br/>
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<h1><a name="recommendations">Recommendations</a></h1>
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<h2>help</h2>
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The PERIPHERAL configuration command will print the documentation string for
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peripherals if the parameter "<tt>help</tt>" is listed. For example, to get
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help for the <tt>monitor_stack</tt> peripheral, insert the peripheral
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using:<br/><br/>
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<tt> PERIPHERAL monitor_stack help</tt><br/><br/>
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This will display the documentation string for the <tt>monitor_stack</tt>
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peripheral and then terminate the build.<br/><br/>
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If there is no documentation string for the peripheral, the
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following message is printed and the build is terminated:<br/><br/>
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<tt> No help for periperal XXX is provided</tt><br/><br/>
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Note: The help message displays the name of the peripheral and the source
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file.<br/><br/>
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</body>
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</html>
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