RS - 422
GND
5
RS - 485 full duplex operation
+TX
2
-TX
8
GND
5
+RX
3
-RX
7
RS - 485 half duplex operation
+TX/+RX
2
-TX/-RX
8
GND
5
Note:
RS 422 is not bi-directional.
9.3.
Standard
Devices cannot send data until they have been addressed by the controlling
computer. A typical command exchange for a device would be:
1.
The computer sends a command.
2.
Devices read the address.
3.
When a device recognizes its address, it decodes the message and
returns an acknowledgment to the computer, along with any data that
was requested.
The serial communications port settings such as number of data/start/stop
bits, parity, etc. are defined subsequently. Every communications exchange
between the controlling computer and a Gamma Vacuum controller using
the standard interface consists of a command packet (sent by the controlling
computer), and a response packet (returned by the remote controller). All
characters in these packets are ASCII. All fields are separated by a space (not
required between the checksum and terminator). Hexadecimal numbers can
be represented in either upper or lower case.
9.4.
Cabling
The SPCe functions as a DTE (Data Terminal Equipment) device. When the
controller is connected to another DTE device (such as a personal computer),
a null modem serial cable is required to connect the devices. The null
modem cable swaps the signal and control lines so that receive and transmit
are properly connected. The controller is equipped with a nine-pin female
(DCE) D-sub connector protruding from the chassis rear.
9.5.
Command packet structure
The command packet is made up of at least five fields and contains
information needed for a remote controller to perform a command. The
04/2021 - ©Gamma
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900026_F
900026_F - Serial (J3) and ethernet (J2) operation
