ZETRON 640 DAPT XTRA, Руководство по установке и ремонту

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Troubleshooting and Repair
130 025-9416
Network Interface Unit ( niu ) Diagnostics
When a down TNPP link is suspected, the niu command provides some useful diagnostics of the
network interface unit. The command can be issued from the plus prompt (+) to determine the
nature of the trouble. In addition, the
-l switch tells the paging terminal to provide information on
the status of each link. For a detailed description of the niu command, see the Model 640 Oper-
ating and Programming Manual (Part No. 025-9417).
TNPP Packet Troubleshooting
The TNPP protocol uses mostly printable ASCII characters transmitted by way of asynchronous
RS-232 data communication. As a result, troubleshooting can be done with a dumb-terminal
emulator on an IBM PC. Problems are often caused by faulty data communications between
TNPP nodes. Inaccurate destination ID programming is another source of difficulties. Both types
of trouble can be detected by monitoring the received and transmitted data with a PC.
A dedicated dumb terminal or PC is needed for TNPP packet troubleshooting (not the same PC
used for MCU and ZLINK operations). Viewcom is an inexpensive terminal emulator program
that works well for this application. Do not use ProComm® or Crosstalk, as these types of
communications packages tend to strip useful control characters from the packets. In addition, a
cable is required to connect the PC's receive data line in parallel with either the transmit (pin 2)
or receive data (pin 3) signal of the TNPP serial port under test.
The TNPP protocol sends RS-232 data packets one after another. The paging packets contain no
carriage returns or line feeds so the data might look a bit confusing. Once you know what to look
for, you can pick out packets easily. All packets start with an SOH (start of header) character,
which looks like an outline of a smiley face.
Note: The TNPP information provided in this section is only meant to be a basic overview
of the specification and its uses. Contact Zetron to order full detailed documentation
on TNPP.
Packet Structure
A TNPP packet is a maximum of 1024 characters long and includes six pieces of information.
The basic structure is shown in Figure 64. The shaded boxes are broken down in the following
subsections.
Data block(s)
(N)
Header
(12)
End flag
(1)
BCC
(2)
STX
(1)
SOH
(1)
Figure 64. General TNPP Packet Structure
The fields are defined as follows:
♦
Start of header flag
SOH “ J .” This field is 1 character long and remains constant.
♦
Header
The header is 12 characters long. It includes the packet addressing
information for routing through the TNPP network. The Model 640 looks
at the destination address and serial number to determine if it should page
the subsequent data blocks. See
Table 24
for details on the header fields.
♦
Start of text flag
STX “ .” This field is 1 character long and remains constant.