Lambda SRS SR475, Руководство по эксплуатации

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1.7 Shutter interface connector 1 – 13
must be provided at the shutter head following the pin-out specified
in Table 1.3. Ground must be provided on pin 2, with chassis ground
on the shield.
Note that standard IEEE-1394 cables are crossover cables that reverse
the signals of pins (3,5) and of (4,6) at the two ends.
1.7.1.1 Serial communication
The features and operation of the SR475 and SR476 remote interface
are discussed in
§
2.
The shutter head serial interface accepts logic-level input (3.3 VDC,
5 VDC tolerant) signals on the RX pin and transmits signals at
3.3 VDC on the TX pin. The protocol is fixed at 19200 baud, with 8
data bits, 1 stop bit, no parity, and no flow control. The polarity of
both signals is such that the start bit and logical “0” are at ground
potential, while the logical “1” is at
= +
3
.
3 VDC.
If the user intends to directly establish serial communication with
the shutter head, independent of an SRS shutter controller, it may
be necessary to use an external signal level converter to translate
between the logic-level signals at the shutter head and (for example)
the voltages and “inverse” polarity of an RS-232 interface.
1.7.1.2 Control signal
The logic-level control signal is the most important input to the shut-
ter head. Unless overridden through the remote interface, a logical
high signal on this input commands the shutter to the open state,
while a low signal commands the shutter to the closed state.
When a change in the input signal is detected, the shutter will imme-
diately begin a transition to the new state if a transition is not already
in progress. A pending state change request will be executed only
after completion of the transition. Changing the level of the con-
trol signal introduces the lowest possible jitter (phase noise) of any
method of initiating a transition, and is the method used by SR470
Series Laser Shutter drivers.
If directly interfacing to the SR475 or SR476 , the control signal ac-
cepts a logic-level input (3.3 VDC, 5 VDC tolerant). To ensure reliable
operation, control pulses to the SR475 or SR476 should be at least
200
μ
s in duration.
SR475 and SR476 Laser Shutters