Fluke 8808A User Manual - Page 67

If Test Fails, How the Meter Processes Input, Input Strings, Input Terminators

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4 Operating the Meter Using the Computer Interface How the Meter Processes Input 6. If the Meter does not respond as indicated, refer to the "If Test Fails" section. If Test Fails If the Meter does not respond as indicated in the "Installation Test for RS-232 Operation" section, perform the following: 1. Ensure all cables are properly connected. See the "Cabling the Meter to a Host or Printer (RS-232)" section earlier in this chapter. 2. Ensure that the communication parameters (baud rate, parity, etc.) on the Meter and host are identical. See the "Setting Communication Parameters (RS-232)" section earlier in this chapter. How the Meter Processes Input The following sections describe how the Meter processes input received from a host or stand-alone terminal. Note In this Chapter, "input" means a string sent to the Meter from a host, and "output" means a string sent to the host from the Meter through the computer interface. Input Strings The Meter processes and executes valid input strings sent by the host. A valid input string is one or more syntactically correct commands followed by an input terminator. When the Meter receives input, it stores it in a 50-byte input buffer. Note Input strings received over the RS-232 interface are not executed or checked for proper syntax until an input terminator is received or the input buffer becomes full. The Meter accepts alphabetic characters in uppercase and lowercase. If a command cannot be understood, the command and the rest of the command line are ignored. Input Terminators When the Meter receives an input terminator, it executes commands on a first-in first-out basis as entered since the last terminator was received. As input characters are processed and executed, space is made available in the input buffer for new characters. In RS-232 applications, if a communication error (parity, framing, overrun) is detected, a device-dependent error is generated and the input string is discarded. If the Meter's input buffer becomes full when it is used with the RS-232 interface, a device-dependent error is generated (see "Event Status and Event Status Enable Register") and the input string is discarded. Valid terminators for the RS-232 interface are: • CR (Carriage Return) • LF (Line Feed • CR LF (Carriage Return/ Line Feed) 4-7

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Operating the Meter Using the Computer Interface
How the Meter Processes Input
4
4-7
6.
If the Meter does not respond as indicated, refer to the “If Test Fails” section.
If Test Fails
If the Meter does not respond as indicated in the “Installation Test for RS-232 Operation”
section, perform the following:
1.
Ensure all cables are properly connected. See the “Cabling the Meter to a Host or
Printer (RS-232)” section earlier in this chapter.
2.
Ensure that the communication parameters (baud rate, parity, etc.) on the Meter
and host are identical. See the “Setting Communication Parameters (RS-232)”
section earlier in this chapter.
How the Meter Processes Input
The following sections describe how the Meter processes input received from a host or
stand-alone terminal.
Note
In this Chapter, “input” means a string sent to the Meter from a host, and
“output” means a string sent to the host from the Meter through the
computer interface.
Input Strings
The Meter processes and executes valid input strings sent by the host. A valid input string
is one or more syntactically correct commands followed by an input terminator.
When the Meter receives input, it stores it in a 50-byte input buffer.
Note
Input strings received over the RS-232 interface are not executed or
checked for proper syntax until an input terminator is received or the input
buffer becomes full.
The Meter accepts alphabetic characters in uppercase and lowercase. If a command
cannot be understood, the command and the rest of the command line are ignored.
Input Terminators
When the Meter receives an input terminator, it executes commands on a first-in first-out
basis as entered since the last terminator was received.
As input characters are processed and executed, space is made available in the input
buffer for new characters. In RS-232 applications, if a communication error (parity,
framing, overrun) is detected, a device-dependent error is generated and the input string
is discarded. If the Meter's input buffer becomes full when it is used with the RS-232
interface, a device-dependent error is generated (see “Event Status and Event Status
Enable Register”) and the input string is discarded.
Valid terminators for the RS-232 interface are:
•
CR (Carriage Return)
•
LF (Line Feed
•
CR LF (Carriage Return/ Line Feed)