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Lexicon, Inc.
RV-8 Serial Communications Protocol
transmitted to the RV-8 will be ignored. Therefore, making the currently transmitted packet, if partially
transmitted invalid.
5.5 RV-8 Hardware Verification
This test verifies the RS232 ports are working by comparing the transmitted signal (at pin 2) to the
received signal (at pin 3). The RV-8 transmits a known test signal just following a power up. The RV-8
monitors the serial port receivers while transmitting the test signal. If the signals are the same, the test
passes. In order to test this circuit, RS232 Wraparound plug(s) are needed and must be installed at the
female D9 connector(s) on the rear panel of the RV-8 labeled "RS232". The wraparound plug shorts pins 2
to 3, allowing for the RV-8 to receive the signal it is transmitting. Once installed, power cycle the RV-8
and verify the following message is displayed on the FPD:
This message is displayed for about 2 seconds before entering normal operating mode. If no messages are
displayed, then both wrap tests failed.
6 Data Link Layer
The data link layer is used to define a transmission packet. The layer appends a header and tail that
encloses the transmitted application packet data. The data link header will contain the start of packet byte
and count of bytes to follow. The data link tail will contain the end of packet byte.
Data Link Header:
Byte Number
Description
First Byte(0)
Start of Packet (SOP)
Byte(1)
DLL Data Count
Application Header:
Byte(2)
Command
APP Data Count (number of application data bytes to
Byte(3)
Follow)
Application Data:
Byte(4)
Data[0]
Byte(5)
Data[1]
...
Data[...]
Last Data Byte -1
Data[Data Count -1]
Data Link Tail:
Last Byte
End of Packet (EOP)
6.1 Errors
If the number of DLL data bytes received is the same as the data count and an EOP has not been received,
the RV-8 responds by transmitting a NAK packet with an error code DC_ERR_INVALID_PACKET. The
RV-8 then continues to look for a SOP byte and will not process the erroneous application packet. The
HOST can use this as an indicator to retransmit the corrupted packet.
In addition, each byte of a packet must be received sequentially and within the INTER_PACKET_TIME.
If any of the bytes within a packet transmission exceeds the INTER_PACKET_TIME, the RV-8 will
respond by transmitting a NAK packet with an error code DC_ERR_INVALID_PACKET. The RV-8 then
© 2005 Lexicon, Inc. All rights reserved.
SERIAL PORT A PASSED
SERIAL PORT B PASSED
Printed on: 07/26/05
Value
0xF1
nn
nn
nn
nn
nn
nn
nn
0xF2
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