EEC SE 7430, User Manual, Page: 84 / 106

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8.1.3. Sending and Receiving Commands
Sending Data
Once a command is sent to the instrument over the 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.

If you write a program, instructions and instructions need to be more than 150 milliseconds
interval between the buffer time (instruction readback time as short as 150 milliseconds)
8.2 GPIB Interface (Opt.109)
This interface is optional on the SE 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 8.4. USB/RS-232/GPIB Command List.
8.2.1 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.
8.2.2 GPIB Address
Each device on the GPIB (IEEE-488) interface must have a unique address. You can set the address