4
4-2
checksum is added to make up the complete Modbus RTU packet.
All Modbus packets are responded to by the Modbus device. The response
packet is either an acknowledgement, an exception message or response data.
Modbus RTU exception messages and transmission errors are saved in the
Modbus Error Register. Response data is held in the output buffer until read
by a VXI-11 device_read, by a raw socket read or by a webserver read. For
Modbus TCP/IP, the response and acknowledgement are encapsulated in the
return packet.
IEEE-488.2 and SCPI commands are parsed and used to set control parameters,
perform an operation or query a parameter. Responses are placed in the output
buffer so they can be returned to the client when the unit is next read. The
other VXI-11.3 commands like Device Clear clears the serial buffers. Device
Trigger has no affect on the 9099. The ReadSTB command causes the 9099
to respond as a GPIB device would to a Serial Poll.
Figure 4-2 9099 block Diagram
Unreg DC
+5V
3.3V
Reg
LAN Reset
ARM9 Processor
RAM
+5
+5
Latch
Diagnostic LEDs
µP BUS
FLASH
LAN
INTFC
Mag
TCP/IP
LAN
RS-422/RS-485
RS-232
1.8V
Reg
5V
Reg
3.3V
Summary of Contents for 9099
Page 20: ...1 16 1 Figure 1 1 9009 Outline Dimensions ...
Page 24: ...1 20 1 Figure 1 3 9099 Certificate of Compliance ...
Page 54: ...3 8 3 Figure 3 1 Status Reporting Structure Flash Configuration Reset ...
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