42
The serial interface is not connected correctly.
Check if the same baud rate is selected for both TH1942 and the controller.
When TH1942 is busy with executing a bus command, TH1942 will not accept any character
from the serial interface at the same time. So the character sent by controller will be ignored. In
order to make sure the whole command is sent and received correctly, the character without a
return character should be sent again by the controller.
4. TH1942 only sends information under following two conditions. The first is when a character is
received normally; TH1942 will send the character back as a handshake. The second is when a
query command is received; TH1942 will send the query response information.
5. Once a query command is received, TH1942 will send the query response information immediately
even if the rest commands have not been finished. So if the command includes two queries, the
controller should read the query responses twice. One query is recommended to be included in a
single command.
6. A query response is sent out in ASCII codes with the preset terminal character.
7. Several query responses will be sent continuously with 1ms interval. The controller should be ready
to receive the responses; otherwise the response information will be lost.
8. The controller should receive the query response terminal character. Otherwise you will confuse a
terminal character with a returned character. At the same time the controller should receive the last
returned character before receiving a query response.
9. For some commands that will take a long time to execute, for example reset command, the
controller should keep waiting to avoid the next command being lost when TH1942 is executing the
former command.
Please refer to Chapter 8 for serial interface program examples.
5.3 Data Format
TH1942 outputs the measurement results using the ASCII character string format via the GPIB bus. The
data format is described in the following Figure 5-3.
SD.DDDDDDESDDD<NL>
S: +/-
D: number 0 to 9
E: exponent sign
(―+‖is
omitted)
<NL>: New Line, ASCII code is 10
Figure 5-3 Data Format
