Changes

== The DAC ==

== The DAC ==

<a name="DAC_interface" id="DAC_interface"></a>

=== DAC interface ===

=== Interface ===

The AD5535 Digital-to-Analog Converter has a three-wire serial interface and an inverted-logic reset signal.  A serial communication transfers one 19-bit word:

The AD5535 Digital-to-Analog Converter has a three-wire serial interface and an inverted-logic reset signal.  A serial communication transfers one 19-bit word:

The three lines of the interface are ''SYNC'', ''SCLK'', and ''D_in''.  A write to the DAC begins with a falling edge of ''SYNC''.  The next 19 bits (counted off by ''SCLK'') are saved into a shift register  The next transfer begins on another falling edge of ''SYNC'', but transfers do not overlap or interrupt.  A minimum of 200ns is required between exchanges.  ''SCLK'' is ignored except during the 19 shift cycles.  The minimum clock pulse width is 13ns high and 13ns low, yielding a maximum frequency of 77MHz theoretically.  In actual fact the maximum clock frequency is 30MHz and the maximum word frequency is 1.2MHz.  For further details on timing and protocol, see the AD5535 data sheet supplied by Analog Devices, in particular "Timing Characteristics" (p.5) and "Functional Description (p.12).

The three lines of the interface are ''SYNC'', ''SCLK'', and ''D_in''.  A write to the DAC begins with a falling edge of ''SYNC''.  The next 19 bits (counted off by ''SCLK'') are saved into a shift register  The next transfer begins on another falling edge of ''SYNC'', but transfers do not overlap or interrupt.  A minimum of 200ns is required between exchanges.  ''SCLK'' is ignored except during the 19 shift cycles.  The minimum clock pulse width is 13ns high and 13ns low, yielding a maximum frequency of 77MHz theoretically.  In actual fact the maximum clock frequency is 30MHz and the maximum word frequency is 1.2MHz.  For further details on timing and protocol, see the AD5535 data sheet supplied by Analog Devices, in particular "Timing Characteristics" (p.5) and "Functional Description (p.12).

<a name="DAC_emulator" id="DAC_emulator"></a>

=== DAC emulator ===

=== Emulator ===

[[Image:DAC Emulator Block.JPG|thumb|DAC emulator functional block diagram]]

[[Image:DAC Emulator Block.JPG|thumb|DAC emulator functional block diagram]]

*** ''Q'': 14-bit output bus

*** ''Q'': 14-bit output bus

<a name="DAC_controller" id="DAC_controller"></a>

=== DAC controller ===

=== Controller ===

[[Image:DAC Controller Block.JPG|thumb|DAC controller functional block diagram]]

[[Image:DAC Controller Block.JPG|thumb|DAC controller functional block diagram]]

== The temperature sensor ==

== The temperature sensor ==

<a name="Temp_interface" id="Temp_interface"></a>

=== Temperature sensor interface ===

=== Interface ===

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:

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:

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.

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.

<a name="Temp_emulator" id="Temp_emulator"></a>

=== Temperature sensor emulator ===

=== Emulator ===

[[Image:Temp Emulator Block.JPG|thumb|Temperature sensor emulator functional block diagram]]

[[Image:Temp Emulator Block.JPG|thumb|Temperature sensor emulator functional block diagram]]

*** ''Ser'': serial output line

*** ''Ser'': serial output line

<a name="Temp_controller" id="Temp_controller"></a>

=== Temperature sensor controller ===

=== Controller ===

[[Image:Temp Controller Block.JPG|thumb|Temperature sensor controller functional block diagram]]

[[Image:Temp Controller Block.JPG|thumb|Temperature sensor controller functional block diagram]]