Rohde & Schwarz R&S SMU200A, Service Manual

Page: 136 / 294

R&S SMU200A Instrument Design and Function Description
1007.9845.82 3.9 E-6
DAC Interface DACIF
The DAC Interface (DACIF) module is a central module of the signal generator. It must always be
present in the instrument. The following functions are provided.
-
Thermal monitoring of the instrument, control of the instrument fans. The ON check of the power
supply unit (overtemperature protection) is also linked logically to these functions. If the
overtemperature protection function has triggered or the DAC Interface module is not inserted, the
power supply of the signal generator does not start.
-
Auxiliary power generation for RF modules and the Universal Coder module (28V)
-
Hardware recognition and checking of the baseband and RF modules. The SPI bus and SER bus
are used for this purpose.
-
Boot controllers of the FPGAs in the other modules; only the FPGA “PIF” of the DAC Interface is
booted from an EEPROM, all other FPGAs are configured from the hard disk. (The booting
procedure is described below.)
-
Output drivers and input amplifiers for all signal generator connections relevant to the baseband
(data, clock, trigger, user).
-
BER and BLER measurement (in the FPGA 'SNIF').
-
USB device functionality: Two USB device chips are available. They are connected to the USB IN
(Type B) socket on the rear panel by means of an integrated hub. The two USB devices have the
following tasks:
USB Remote Control: This device is used to remotely control the signal generator and to load
the firmware.
USB Modulation Data In: This device is used to load data to be modulated by the signal
generator, from an external PC. The data is then sent internally to the CODER.
-
Slot for two DAC boards. The digital data (I+Q) is passed from the motherboard to the DAC boards
without being processed further. A selection circuit is provided for the analog I/Q output.
-
Clock generation for the baseband (100 MHz) and for the DAC boards (400 MHz). A synchronization
circuit ensures precise temporal reference of the converters to the DAC boards.
-
LF generator: Generation of a CW signal up to 1 MHz. This signal is sent to the rear panel and the
RF modules.
-
Instrument diagnosis: An A/D converter is used to read out operating voltages and calibration values
of the individual modules. This allows the voltage supply for the modules and the internal voltages of
a particular module to be checked during the self test.
Booting procedure for other modules:
The DAC Interface boots the FPGAs on the other modules. The name and version are read out of the
EEPROM of the target module for this purpose. They are used to form the name of a key in the registry.
The value of this key is the file to be loaded.
The version of the loaded FGPA can be shown in the version display. If 0.0.0 is displayed for a chip,
this chip could not be loaded.