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Line 15: − + − == The temperature sensor == − − The VHDL files can be found [http://zeus.phys.uconn.edu/halld/tagger/electronics/design-6-2007/Temp_VHDL.zip here]. − − === Interface (T) === − − The AD7314 temperature sensor uses a four-wire interface related to (and compatible with) the [http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus SPI bus] protocol. The wires are: − − * ''SCLK'': Serial Clock (input), clock line supplied by external source − * ''SDI'': Serial Data In (input), data input line − * ''SDO'': Serial Data Out (output), data output line − Note that the input/output notations are for slave devices (such as the temperature sensor) but are reversed for master devices (such as the FPGA). Proper SPI protocol flips the I/O polarity of ''CE'' and ''SCLK'' and crosses the ''SDI'' and ''SDO'' lines so that ''SDI'' is an input on every device and ''SDO'' is always an output. To maintain simplicity in wiring conventions we are not using proper SPI protocol, but are calling the slave input/master output line ''SDI'' and the slave output/master input line ''SDO'' so that the ''SDI/O'' notations are proper for slaves. The maximum clock rate is no higher than 10MHz. The interface, having separate input and output lines, is full-duplex; in fact the temperature sensor is unable to function in half-duplex mode. Outputs from the temperature sensor change on rising edges of ''SCLK'', but inputs are latched on falling edges. − − There is only one write operation to the temperature sensor and that is used to direct the temperature sensor to enter power-down mode. We do not plan to use this mode, so the ''SDI'' input on the temperature sensor will be tied to ground. − − A read operation occurs during a 16-cycle pulse of ''CE''. The first transmitted bit will be zero, followed by ten bits of temperature data (MSB first). The remaining five bits are copies of the final data bit. After ''CE'' goes low ''SDO'' goes into a high-Z state. Temperature data is given in degrees Celsius. The format is two's-complement with two decimal places; in essence it is standard two's-complement, then the result must be divide by four after converting to decimal. − − === Emulator (T) === − − − − The functional block diagram for the emulator is shown to the right. The blocks are: − * '''Error Flag''' − ** The error flag goes high if the enable line is high for 1-15 or 17+ cycles. It resets to low any time the enable line goes back to high. It is used to notify of a "bad" transmission (not 16 cycles long). − ** inputs − *** ''Clk'': clock − *** ''Rst'': asynchronous, active-low reset − *** ''En'': enable − ** outputs − *** ''Err'': error flag − * '''Shift Reg''' − ** An 11-bit, parallel-in, serial-out shift register that loads when not shifting. − ** inputs − *** ''Clk'': clock − *** ''Rst'': asynchronous, active-low reset − *** ''Sh/Ld'': active-high shift, active-low load − *** '' Par(10:0)'': 11-bit parallel input bus − ** outputs − *** ''Ser'': serial output line − − === Controller (T) === − − [[Image:Temp Controller Block.JPG|thumb|Temperature sensor controller functional block diagram]] − − The functional block diagram for the controller is shown to the right. The blocks are: − * '''Counter''' − ** Counts a cycle of 17 pulses; holds ''En'' high for 11 pulses, holds ''CE'' high for 16 pulses. − ** inputs − *** ''Clk'': clock − *** ''Rst'': asynchronous, active-low rest − *** ''Go'': trigger to begin cycle − ** outputs − *** ''CE'': serial chip enable − *** ''En'': internal shift enable − * '''Delay''' − ** Delays input by one clock cycle. − ** inputs − *** ''Clk'': clock − *** ''D'': input signal − ** outputs − *** ''Q'': output signal − * '''Shift Reg''' − ** A 10-bit, serial-in, parallel-out shift register. − ** inputs − *** ''Clk'': clock − *** ''Rst'': asynchronous, active-low rest − *** ''D'': input signal − *** ''En'': shift enable − ** outputs − *** ''Q'': 10-bit output bus
no edit summary
* [[Programming the DAC]]
* [[Programming the DAC]]
* [[Programming the temperature sensor]]
* [[Programming the temperature sensor]]
* [[Programming the ADC]]
* ''CE'': Chip Enable (input), positive logic enable for ''SCLK''
[[Image:Temp Emulator Block.JPG|thumb|Temperature sensor emulator functional block diagram]]
== The ADC ==
== The ADC ==