Agilent Technologies AGC-100, Manual

Page: 54 / 96

Vacuum Gauge Controller AGC-100
54
5 Communication Protocol (Serial Interface)
The AGC-100 communicates with a computer via virtual serial interfaces (COM
ports). Thus the user software can access the AGC-100 via USB Type B or via
Ethernet interface.
The corresponding driver for the virtual COM port is installed automatically, when
the AGC-100 is connected to a computer via the USB Type B interface. If the driver
is not installed automatically, it can be downloaded from the FTDI website
(www.ftdichip.com/Drivers/VCP.htm).
The installed virtual COM port appears as additional serial interface in the device
manager of the computer.
With the Ethernet Configuration Tool a virtual serial interface (COM) can be as-
signed to an IP address. In addition, it allows configuration of the Ethernet interface
via a computer (
→
 86).
The installed virtual COM port appears as additional serial interface in the device
manager of the computer.
When the AGC-100 is put into operation, it starts transmitting measured values in
intervals of 1 s. As soon as the first character is transferred to the AGC-100, the
automatic transmission of measured values stops. After the necessary inquiries or
parameter modifications have been made, the transmission of measured values
can be started again with the
COM
command ( →

58).
The data transmission is bi-directional, i.e. data and control commands can be
transmitted in either direction.
1 start bit, 8 data bits, no parity bit, 1 stop bit, no hardware handshake
The following abbreviations and symbols are used:
Symbol Meaning
HOST
Computer or terminal
[...] Optional elements
ASCII American Standard Code for Information Interchange
Dez Hex
<ETX> END OF TEXT (CTRL C)
Reset the interface
3 03
<CR> CARRIAGE RETURN
Go to beginning of line
13 0D
<LF> LINE FEED
Advance by one line
10 0A
<ENQ> ENQUIRY (CTRL E)
Request for data transmission
5 05
<ACK> ACKNOWLEDGE
Positive report signal
6 06
<NAK> NEGATIVE ACKNOWLEDGE
Negative report signal
21 15
"Transmit": Data transfer from HOST to AGC-100
"Receive": Data transfer from AGC-100 to HOST
After each ASCII string, the HOST must wait for a report signal (<ACK><CR><LF>
or <NAK> <CR><LF>).
The input buffer of the HOST must have a capacity of at least 32 bytes.
Communication via USB Type B
interface
Communication via Ethernet
interface
5.1 Data Transmission
Data format
Definitions
Flow Control