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5.4 RV8 Receive Buffer
The RV8 has an internal receive buffer. The buffer is 256 Bytes and will transmit a NAK packet
with an error code of DC_ERR_BUFFER_FULL to the HOST if the buffer is full. If the buffer is
full, all data transmitted to the RV8 will be ignored. Therefore, making the currently transmitted
packet, if partially transmitted invalid.
5.5 RV8 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 RV8 transmits a known test signal just following a power up.
The RV8 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 RV8 labeled "RS232".
The wraparound plug shorts pins 2 to 3, allowing for the RV8 to receive the signal it is
transmitting. Once installed, power cycle the RV8 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
First Byte(0)
Byte(1)
Application Header:
Byte(2)
Byte(3)
Application Data:
Byte(4)
Byte(5)
...
Last Data Byte -1
Data Link Tail:
Last Byte
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 RV8 responds by transmitting a NAK packet with an error code
DC_ERR_INVALID_PACKET. The RV8 then continues to look for a SOP byte and will not
SERIAL PORT A PASSED
SERIAL PORT B PASSED
Description
Start of Packet (SOP)
DLL Data Count
Command
APP Data Count (number of application data bytes to
Follow)
Data[0]
Data[1]
Data[...]
Data[Data Count -1]
End of Packet (EOP)
RV-8 Serial Communications Protocol
Value
0xF1
nn
nn
nn
nn
nn
nn
nn
0xF2
7
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