Channel control ASIC for the CMS hadron calorimeter front end readout module Page: 2 of 4
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" Check QIE CapIDs to see that QIEs are synchronized.
" For test purposes, force QIEs into fixed range mode
instead of auto ranging mode.
" Adjust QIE pedestal level to correct for HPD leakage.
" Reset QIEs.
" Place QIE in calibration mode (special high sensitivity
ADC range) for calibration with a radioactive source.
" Issue test pulse triggers of programmable polarity for
either HPD or PMT operation to the QIEs.
" Flag bunch crossing counter check error.
" Provide test pattern registers to check operation of DAQ
and check the optical data links.
As can be seen from the preceding list of functions,
operation of the CCA is closely tied to that of the QIEs.
Figure 4 shows the connections between 1/2 of a CCA, and a
QIE. The common control signals for the full CCA are at the
top of the figure. The specific CCA address is set by 6 lines
called RBX_A that are programmed by hard wire connections
on the printed circuit board.
CC -BX A 8i CNTRL
Control LHC Clock 'B TATA 18
Signals BCZero SENDFF *
TEST PULSES \
QIE EXPa 2,
QIE QE CAPIDa 2
HPD integrated Q CLKa 2 Repeated
or PMT FADC QIE 1/2 for 2nd QIE
FED DAca q=
EN QIE RANGE
Tb second QIE
Figure 4: Signals to and from CCA
Operation of the CCA is examined by looking at four
different sets of circuits.
A. RBX interface and registers
The RBX interface bus gets its name from the HCAL
Readout Boxes. The RBX interface is a 2-wire
communication interface that is similar to the well-known I2C
interface. All data is downloaded, 8 bits at a time, through the
RBXDATA line and clocked with the RBX_CLK line.
Information is expected to be downloaded or read back at 100
Kbits/sec. RBX data is written to, or read from, a Pointer
Register or a Data Register. The Pointer Register points to 1
of 28 eight bit internal registers as shown in Figure 5. The
Data Register contains data to be written or read from the
pointer address location. After each data transfer, the Pointer
Register automatically points to the next internal register, to
reduce chip communication overhead. For reliability, all
registers are designed with SEU tolerant flip-flops .
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dXo DATA RS1frie.r A4eees CALffi MODE
RB DAT Dam ; (8d~ffrent7E NGE 2
-o o- q LSlI
Resgeter QIgf CLE mo CL~b
3setb 6eesee PdselA PEoochb
Figure 5: RBX and control register space
Figure 6 shows a typical set of instructions to download
information to the CCA via the RBX bus. The first word
contains the chip address, a bit (0) to choose the Pointer
Register and a bit (0) to indicate a Write command. The
second word uses 6 bits to indicate the internal CCA register
address to be loaded in the Pointer Register. The third word
again presents the chip address, sets a bit (1) to choose the
Data Register, and a bit (0) to once again indicate a Write
command. The next word is the data to be loaded into the
internal register selected by the Pointer Register. Data can
then be loaded into subsequent internal registers with each
RBX bus cycle.
4 A7:A0 (Data to be loaded into nth Internal Register)
5 A7:AO (Data to be loaded into n+1 Internal Register)
Figure 6: Typical data download to CCA via RBX bus
Figure 5 shows the 28 internal CCA control registers. The
functions of the registers are as follows:
" Control Register - 1 register to set various internal CCA
controls and control settings for QIEs.
" Alignment Control Registers - 2 registers, one for each
of two QIEs for the purpose of selecting various timing
options to permit channel operation with timing
differences up to 58 nsec.
" Pedestal DAC Register - 1 register for two QIEs
wherein 4 bits are used for each QIE to set a pedestal in
the QIE to correct for HPD leakage currents.
" QIEs DLL Tap Setting Register - 1 register to program
DLL delay for QIEa in 1 nsec increments from 0 to 25
A7:A2 (Chip address) A1=m (Pointer) A0=0 (write)
A7:A2 (Internal register address loaded into Pointer Register)
A7:A2 (Chip address) A1=1 (Data) A0=0 (Write)
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al., Ray Yarema et. Channel control ASIC for the CMS hadron calorimeter front end readout module, article, September 26, 2002; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc742967/m1/2/: accessed February 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.