LDI DIGISONDE 4D - Common Packet Format

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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
SECTION 5 - SYSTEM SOFTWARE – ANNEX A 5-29
Table 5A- 2: Primitive Field Types
Abbreviation
Byte Len
Description
INT8U
1
8 bits unsigned
INT8S
1
8 bits signed
INT16U
2
16 bits unsigned
INT16S
2
16 bits signed
INT32U
4
32 bits unsigned
INT32S
4
32 bits signed
INTU ACD
Variable, 1- 15
Unsigned integer represented as ASCII Coded Decimal
Each decimal digit of integer number takes one byte of external memory and its ASCII code will be
saved there. If length of the field is larger than length of bytes occupied by integer number then this
number has to be shifted to the right edge of the field and has to be padded either by ASCII code of ‘0’
or ASCII code of SPACE.
INTS ACD
Variable, 1- 15
Signed integer represented as ASCII Coded Decimal
Each decimal digit of integer number takes one byte of external memory and its ASCII code will be
saved there. ASCII code of sign can be saved as first byte. If length of the field is larger than length of
bytes occupied by integer number then this number has to be shifted to the right edge of the field and has
to be padded either by ASCII code of ‘0’ or ASCII code of SPACE.
5:74. Any of these basic types can be used to construct an array, for example, INT8U array.
COMMON PACKET FORMAT
5:75. Generally, all DPS V6 packets consist of the following 5 sections (Table 5A- 3):
• Sync Pattern, used for frame synchronization in the lossy communication environments. Sync pattern
for DPS V6 is 3 byte sequence 0xFEFA31
3
.
• Length (byte count of the packet contents, including all packet elements from sync pattern to the
checksum)
• Packet Type, used to distinguish it from other packets requiring different actions
• Packet Data (Data Section of Packet)
• Checksum (XOR of all bytes in the packet)
5:76. Length, Packet Type and Packet Data constitute the packet Payload.
Table 5A- 3: Common Packet Format
Byte
Offset
Byte
Len
Mnemonic
Description
Units
Type
Range
0
3
SYNC
Sync Pattern
0xFE, 0xFA, 0x31
-
INT8U
Constant
3
2
LENGTH
Length of packet including SYNC, LENGTH,
TYPE, DATA, and CS
byte
INT16U
0..65535
5
1
TYPE
Type of packet
-
INT8U
0..255
6
Variable
DATA
Packet Data
byte
INT8U array
-
Last
1
CS
Checksum
byte
INT8U
0..255
3
FEFA30 header is used for RPI, and FEFA32 header is used for TNT.