Stanford Research Systems SR810 Manual page 136

Circuit Description
Aux A/D inputs. The Aux inputs are multiplexed so
that each input is read every four cycles. The two
digital output streams are buffered by U406 and
sent to the DSP board.
I/O INTERFACE
The Analog Input Board communicates with the
CPU Board via its I/O Interface. U504 and U506
are simple latches which hold configuration data
for the analog board. They are written via the
isolated data bus from the DSP board. This data
bus is active only when the Analog board is
addressed. This prevents noise from the CPU and
DSP boards from entering the Analog Board.
Timing signals for the A/D Converter are buffered
by U406.
POWER
Several voltages are generated on the Analog
Input Board locally. ±15 V is generated for most of
the analog IC's. A dedicated ±15 V supply is also
generated for the front-end amplifier. ±5.6 V is
generated for the digital circuitry as well as some
of the drivers. The A/D Converter has its own ±5 V
supply.
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