Application of CPLD

1
SH1.5 1-P-194
Application of CPLD for the Mexico Solar Neutron
Telescope
Takashi Sako, Y.Muraki, and N.Hirano
Solar-Terrestrial Environment Laboratory, Nagoya
University, Japan
(sako_at_stelab.nagoya-u.ac.jp)
Abstract We have adapted the Complex
Programmable Logic Device (CPLD) technique for
the direction measurement circuit used in the
Mexico Solar Neutron Telescope. Before designing
this application, we performed some basic tests
for XILINX CPLD XC95108. The device satisfied
our requirements for the Solar Neutron Telescope,
that is, a response for a high frequency input,
a response for a narrow width pulse input, and no
or negligible jitter of the delay in the circuit.
The use of such programmable device enables us
to upgrade the detector in future and reduces
circuit design errors.
1. Solar Neutron Telescope In the solar
neutron telescope, an incoming neutron is
converted into a proton in the plastic
scintillators. The direction of the recoil
proton is measured using proportional counters
(PRCs). Detail of the Solar Neutron Telescope
in Mexico is presented by J.F.Valdes-Galicia
et al. (SH1.5)
Fig1. The Solar Neutron Telescope installed in
Mexico.
Photo1. The direction measurement circuit
composed of conventional TTL logic ICs. Photo2.
Same circuit as Photo1 but produced using CPLD.
2. CPLD To measure the direction of the recoil
proton as illustrated in Fig.1, a complicated
(but simple logic) circuit is necessary
(Photo.1). However Complex Programmable Logic
Device (CPLD) realizes this circuit with only
one chip (Photo.2). Designed circuit is
easily downloaded from a PC (Photo3.) The
device used in this study is XILINX 95108,
having 2400 logic gates and 108 I/O pins.
Photo3. Download process from PC to the device.
3. Basic Tests The device correctly functioned
for the input pulse of 10nsec width. For high
frequency input, we confirmed a correct
response up to 2MHz input. (Test stopped at this
frequency where no problem found.) In-chip
delay was always constant at 5nsec for various
number of successive logic gates up to 4. All
these properties are satisfactory to use this
device for the Solar Neutron Telescope.
4. Applications The direction measurement
circuit for the Mexico Solar Neutron Telescope
is produced using CPLD and some test data were
obtained (Fig.3). The continuous observation
will be started in September. The technique of
CPLD (or FPGA) will be available future
experiment like the Super Solar Neutron
Telescope presented by Sako et al. (SH1.5).
Fig.2 Left Intensity map of muon. Zenith angle
effect is seen. Right 3-day stability for 5
of 25 direction channels.