75
7.1.3. Sending and Receiving Commands
Sending Data
Once a command is sent to the instrument over the USB/RS-232 bus the instrument
will send one of two responses. If the transfer was recognized and completed the
instrument will return with 06 hex or 6 decimal, the Acknowledge (ACK) ASCII control
code. If there is an error with the command string that is sent, the instrument will
respond with 15 hex or 21 decimal, the Not Acknowledge (NAK) ASCII control code.
The ACK or NAK response allows for software handshaking to monitor and control
data flow.
Receiving Data
When requesting data from the instrument it will automatically send the data back to
the controller input buffer. The controller input buffer will accumulate data being sent
from the instrument, including the ACK and NAK response strings, until it has been
read by the controller.
7.2. GPIB Interface
This interface is optional on the 620L and provides all of the control commands and
parameter setting commands of the USB/RS-232 interface along with 488.2 Common
Commands and SRQ capability. All commands can be found in section
7.4. USB/RS-
232/GPIB Command List
.
7.2.1. GPIB Connector
Connection is usually accomplished with a 24-conductor cable with a plug on one end
and a connector at the other end. Devices may be connected in a linear, star or a
combination configuration.
The standard connector is the Amphenol or Cinch Series 57 Microribbon or AMP
CHAMP type. The GPIB uses negative logic with standard transistor-transistor logic
(TTL) levels. When DAV is true, for example, it is a TTL low level (
0.8 V), and when
DAV is false, it is a TTL high level (
2.0 V).
Restrictions and Limitations on the GPIB
A maximum separation of 4 m between any two devices and an average
separation of 2 m over the entire bus.
A maximum total cable length of 20 m.
No more than 15 device loads connected to each bus, with no less than two-
thirds powered on. For example 1 GPIB controller and a maximum of 14 GPIB
instruments.
Note:
A bus extender, which is available from numerous manufacturers, is
available to overcome these limitations.
Содержание 620L
Страница 99: ...93 ...
Страница 105: ...99 The following figure shows how to connect the 620L to an Associated Research HypotULTRA III tester ...
Страница 106: ...100 The following figure shows how to connect the 620L to an Associated Research Omnia 8104 tester ...
Страница 123: ...117 From this screen four parameters may be accessed MAC Address Barcode I P Autostart and previous page ...
Страница 125: ...119 After the barcodes are scanned press TEST to initiate the test sequence Pressing RESET will abort the TEST sequence ...