Cropico DO6, Руководство пользователя

Страница: 50 / 107

DO6 Handbook
Jan 2006 50 of 107 pages
7.2.2 Interface parameters
The interface parameters can be set in menu 150 Interface.
Baud rates:
300, 600, 1200, 2400, 4800, 9600(*), 19200, 38400, 56000, 57600
Data bits: 7 or 8(*)
Stop bits: 1(*) or 2
Parity: none (*), even, odd
Block check: Enabled(*) or Disabled
(*) Default setting after initialisation
The instrument waits for a command in the form: <STX>command1<LF><ETX>
<STX>: ASCII value 02
Command 1: SCPI command without query form
<LF>: ASCII value10
<ETX>: ASCII value 03
7.2.3 Communications protocol
Control characters:
<STX> 0x02 => Start of text
<ETX> 0x03 => End of enquiry
<ENQ> 0x05 => Enquiry
<ACK> 0x06 => Acknowledge
<S> 0x20 => Space
<NAK> 0x15 => Not acknowledged
<LF> 0x0A => Line feed
<EOT> 0x04 => End of transaction
<NUL> 0x00 => NULL character
The ANSI standard X3.28-1976 Subcategory 2.5, A4 is used as the communications protocol.
This standard is used in systems in which a number of secondary stations exist in a nonswitched
multipoint connection, and all commands are sent by a control station. Only one transmitter
(master) and one receiver (slave) are ever active on the bus at one time. One station is the control
station. The control station is given master status and sends commands to a selected slave station,
or relinquishes its master status to a secondary station and assumes slave status to receive data. A
connection between two secondary stations is not allowed. The control station monitors the
connection continuously.
7.2.4 Establishing a connection
Before a connection is established, the control station has master status and none of the secondary
stations have slave status. The connection can be established in two different ways:
1. Selection with response
In this case, addressing the device does not take place in the same communications step as
sending the command. This method is useful when you want to send several commands to
the same device and then retrieve the responses at one go (See communications example in
section 8.16)