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4.1
RS-232C SERIAL INTERFACE
The Models 818 and 819 feature a serial RS-232C interface which allows communication with a host
computer (see Table 4-1 below):
Table 4-1. Model 818/819 RS-232C Interface Specifications
Transmission: Three Wire
Connector: RJ-ll Modular Socket
Timing Format: Asynchronous
Transmission Mode: Half Duplex
Baud Rate: 300
4.2
INTERFACE COMMANDS
The paragraphs below define RS-232C Interface Commands and their format. Enter switch and channel IDs
as integers (no decimal point). Enter temperatures to 0.1 degrees. If entered with greater precision, they
truncate to the nearest 0.1 degree. Enter temperatures with or without a decimal point. For example, any of
the following are valid temperature entries: 5, 5.0, 24, 98.3, 235. Temperature is bounded by upper and lower
sensor limits listed in Table 3-1.
4.2.1
Display and Alarm Parameter Commands
F0
Select Display Units
Input:
F0K, F0C, F0F, or F0V
Returned: Nothing.
Remarks: Sets display units to Kelvin (K), Celsius (C), Fahrenheit (F), or Volts (V).
H
Set High Alarm Setpoint.
Input:
Model 818: H<Temperature>, Model 819: <Channel>H<Temperature>
Returned: Nothing.
Remarks: Sets the High Alarm setpoint. Channel = 0 to 4. Example: For a setpoint of 300° on the
Model 818, type H300. For a setpoint of 31.2° on channel 3 on the Model 819, type 3H31.2.
Select temperature units from the unit keyboard or by using the F0 command.
L
Set Low Alarm Setpoint.
Input:
Model 818: L<Temperature>, Model 819: <Channel>L<Temperature>
Returned: Nothing.
Remarks: Sets the Low Alarm setpoint. Channel = 0 to 4. Example: For a setpoint of 21.1° on the
Model 818, type L21.1. For a setpoint of 21.1° on channel 3 on the Model 819, type 3L21.1.
Select temperature units from the unit keyboard or by using the F0 command.
R
Reset Alarms
Input:
R
Returned: Nothing.
Remarks: Resets the alarms.
Remote Operation
Lake Shore Model 818 / 819 Cryopump Monitor User's Manual
CHAPTER 4
REMOTE OPERATION
Bits per Character: 7 (not including start, stop or parity bits)
Parity Type: odd
Number of Stop Bits: 1
Data Interface Levels: Transmits/Receives using EIA voltage levels
4-1
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