48
Chapter 7. Digital I/O
7.5
TTL switching
A versatile feature of the
ARF/XRF
is the ability to rapidly switch
the
RF
in response to an external input.
This enables rapid pulse-
generation in synchronisation with other laboratory devices.
In high-power units, the amplifiers can be controlled separately from
the
RF
signal using the following commands:
ON,1
Turn on both signal and amplifiers (slow)
OFF,1,SIG
Switch off signal only (fast)
ON,1,SIG
Switch on signal only (fast)
ON,1,POW
Turn on amplifiers only (slow)
This behaviour can also be controlled through the
TTL
inputs of the
DB15
connector,
labelled
CHx-OFF
and
CHx-ON
(see
7.1).
Both
of
these inputs are active
LOW
, and have the following behaviour:
CHx-ON
When the output is off, pulling this pin
LOW
will switch
both
the
RF
signal and amplifiers
ON
(
NSB
mode only).
Does not
need enabling in software, has no effect when disconnected.
CHx-OFF
When
enabled
(see
below),
the
RF
signal
will
be
disabled
unless
this pin is pulled
LOW
. If disconnected or
TTL HIGH
, no
output is generated.
Does not affect the
RF
amplifiers.
Because the
CHx-OFF
input disables the
RF
output by default, it must
be explicitly enabled using software commands as follows:
EXTIO,MODE,1,OFF,TOGGLE
Sets
CHx-OFF
to
TOGGLE
mode: the
RF
is off whenever the input
is
HIGH
and the output is enabled whenever the input is
LOW
.
Can be used for generating rapid externally-controlled pulses.
EXTIO,MODE,1,OFF,LATCH
Sets
CHx-OFF
to
LATCH
mode:
if the
OFF
input goes
HIGH
, the
output will be disabled and remain disabled.
The output can
then
only
be
re-enabled
by
taking
the
input
LOW
and
then
Содержание ARF021
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Страница 26: ...16 Chapter 3 Communications ...
Страница 44: ...34 Chapter 5 External modulation ...
Страница 50: ...40 Chapter 6 PID stabilisation ...
Страница 64: ...54 Chapter 7 Digital I O ...
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