ProStar325 Service Manual
Publication date 8 May 2003
77
The use of an eight-layer PWB ensures that radiation from the
printed tracks is reduced, because the tracks act as microstrip
transmission lines relative to the contiguous groundplane.
Small ferrites have been fitted to many signal lines that leave the
Processor PWB. These inductive devices and the capacitance on
the lines filter out higher frequency components, reducing
emission of offending radio frequency spectra. Ferrites on input
lines also improve input noise reduction and immunity from
external interference.
To reduce edge transition speeds (and subsequent radiated noise
levels) on the digital lines, the slew rate and drive currents on the
Field Programmable Gate arrays have been set to the minimum
required for the design to work properly.
4.3.1
Processor PWB functions
The Processor PWB is based on a 32-bit microcontroller type
AMD Elan SC520, 133MHz with 4MB field upgradeable flash
memory. Also on board is 128MB of SDRAM. Software contained
in the flash memory gives the microprocessor multitasking
capabilities which enable a number of operations to be carried out
simultaneously.
A thumbwheel switch and two seven-segment displays are
provided for diagnostic control and reporting.
These tasks are executed by the processor PWB -
Wavelength
drive
Photometric signal measurement
Data
buffering
Timing control for MUX, ADC and preamp integrators
Source lamp selection and control
Ethernet TCP/IP communications
Real time synchronization of dual channel analog outputs
Service diagnostic tests
Programmable Sync I/O signals
Controls four programmable relays & peak sense relay
Display detector status through front panel dual colored
LED’s
Setting the Programmable Gain Amplifier
4.3.1.1
Microcontroller
The Processor PWB is controlled by a 32-bit microcontroller U11,
clocked at 33MHz by crystal oscillator Y1. It works off 3.3Volts
with a core Vcc=2.5V.
The microcontroller is responsible for the following;
ROM/Flash memory/EEPROM control
Clock, Reset and timing signals
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Summary of Contents for ProStar 325 UV-Vis
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