SFC6400A/SFC1450A Synthesized Frequency Upconverter
User Interfaces
TM106 – Rev. 1.1
4-25
<OPCODE>
- The Operation Code field contains a number that identifies the message type
associated with the data that follows it. Acknowledgment and error codes are returned in this field.
This field is 2 Bytes for the SFC6400A/SFC1450A protocol.
<...DATA..>
- The Data field contains the binary, data bytes associated with the
<OPCODE>. The number of data bytes in this field is indicated by the <BYTE COUNT> value.
<CHECKSUM>
- The checksum is the modulo 256 sum of all preceding message bytes, excluding
the <SYN> character. The checksum determines the presence or absence of errors within the
message. In a message block with the following parameters, the checksum is computed as shown
below in Table 4-4.
Table 4-4. Checksum Calculation Example
BYTE FIELD
DATA CONTENT
RUNNING CHECKSUM
<BYTE COUNT> (Byte 1)
00h = 00000000b
00000000b
<BYTE COUNT> (Byte 2)
02h = 00000010b
00000010b
<SOURCEID>
F0h = 11110000b
11110010b
<DESTINATION ID>
2Ah = 00101010b
00011100b
<FSN>
09h = 00001001b
00100101b
<OPCODE> (Byte 1)
00h = 00000000b
00101000b
<OPCODE> (Byte 2)
03h = 00000011b
00101000b
<DATA> (Byte 1)
DFh = 11011111b
00000111b
<DATA> (Byte 2)
FEh = 11111110b
00000101b
Thus, the checksum is 00000101b; which is 05h or 5 decimal. Alternative methods of
calculating the checksum for the same message frame are:
00h + 02h + F0h + 2Ah + 09h + 00h + 03h + DFh + FEh = 305h.
Since the only concern is the modulo 256 (modulo 100h) equivalent (values that can be
represented by a single 8-bit byte), the checksum is 05h.
For a decimal checksum calculation, the equivalent values for each information field are:
0 + 2 + 240 + 42 + 9 + 0 + 3 + 223 + 254 = 773;
773/256 = 3 with a remainder of 5. This remainder is the checksum for the frame.
5 (decimal) = 05h = 0101b = <CHECKSUM>
4.4.2.3 Frame Description and Bus Handshaking
In a Monitor and Control environment, every message frame on a control bus port executes as a
packet in a loop beginning with a wait-for-SYN-character mode. The remaining message format
header information is then loaded, either by the M&C computer or by a subordinate piece of
equipment requesting access to the bus. Data is processed in accordance with the OPCODE, and
the checksum for the frame is calculated. If the anticipated checksum does not match then the
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Страница 82: ...Rear Panel Interfaces SFC6400A SFC1450A Synthesized Frequency Upconverter 5 10 TM106 Rev 1 1 ...
Страница 84: ...Maintenance and Troubleshooting SFC6400A SFC1450A Synthesized Frequency Upconverter 6 2 TM106 Rev 1 1 ...
Страница 90: ...Technical Specifications SFC6400A SFC1450A Synthesized Frequency Upconverter 7 6 TM106 Rev 1 1 ...
Страница 96: ...Appendix A SFC6400A SFC1450A Synthesized Frequency Upconverter A 6 TM106 Rev 1 1 ...
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Страница 121: ...Appendix B SFC6400A SFC1450A Synthesized Frequency Upconverter B 4 TM106 Rev 1 1 1 Second 0 59 ...
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Страница 149: ...Appendix C SFC6400A SFC1450A Synthesized Frequency Upconverter C 20 TM106 Rev 1 1 ...
Страница 153: ...Glossary SFC6400A SFC1450A Synthesized Frequency Upconverter G 4 TM106 Rev 1 1 M C Monitor and Control ...
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