Hioki RM3542, Инструкция по эксплуатации, Страница: 114 / 218

9.5 Communication Methods
108

Compound Command Header Omission
When several commands having a common header are combined to form a compound com-
mand (e.g.,
:CALCulate:LIMit:REFerence and :CALCulate:LIMit:PERCent ),
if they are written together in sequence, the common portion (here, :CALCulate:LIMit: )
can be omitted after its initial occurrence.
This common portion is called the “current path” (analogous to the path concept in computer
file storage), and until it is cleared, the interpretation of subsequent commands presumes that
they share the same common portion.
This usage of the current path is shown in the following example:
Full expression
:CALCulate:LIMit:REFerence
1.0E+3;:CALCulate:LIMit:PERCent 1.0,-1.5
Compacted expression
:CALCulate:LIMit:REFerence 1.0E+3;PERCent 1.0,-1.5
The current path is cleared when the power is turned on, when reset by key input, by a colon
“:” at the start of a command, and when a message terminator is detected.
Standard command messages can be executed regardless of the current path.
They have no effect upon the current path.
A colon “:” is not required at the start of the header of a Simple or Compound command. How-
ever, to avoid confusion with abbreviated forms and operating mistakes, we recommend
always placing a colon at the start of a header.

Output Queue
Response messages are stored in the output queue until read by the controller. The output
queue is also cleared in the following circumstances:
• Power on
• Device clear
• Query Error
The output queue capacity of the instrument is 64 bytes. If response messages overflow the
buffer, a query error is generated and the output queue is cleared.
Also, with GP-IB, if a new message is received while data remains in the output queue, the
output queue is cleared and a query error is generated.

Input Buffer
The input buffer capacity of the instrument is 256 bytes.
If 256 bytes are allowed to accumulate in this buffer so that it becomes full, the GP-IB inter-
face bus enters the waiting state until space is cleared in the buffer.
The RS-232C interface will not accept data beyond 256 bytes.
This portion becomes the current path, and can be omitted from the messages immedi-
ately following.
Output Queue and Input Buffer
Ensure that the no command ever exceeds 256 bytes.