Welch Allyn Connectivity Server - Programmers guide - Manual (Page 16)

12 HL7 standard protocols Welch Allyn Connectivity Server
HL7 low-level protocol
This section describes the low-level format of HL7 packet frames.
Packet frames
HL7 frames that are exchanged between the server and the client describe both sent and
received data.
HL7 segment-level protocols
This section describes HL7 message hierarchy and delimiters, segment notation and
date/time format.
Message hierarchy and message delimiters
Segment notation
Table 5. HL7 packet frame: low-level format
Packet description Content Size (bytes)
Start block 0x0B ASCII <VT> 1
Body variable bytes variable
End block 0x1C ASCII <FS> 1
Carriage return 0x0D ASCII <CR> 1
Group
Groups
Segments
| Fields |
&components&
^subcomponents^
Table 6. HL7 segment notation: mandatory, optional and repeating
Notation example Definition
PID This segment is mandatory.
[PID] This segment is optional.
{IN1} This segment is mandatory, and it can repeat.
[{NK1}] This segment is both optional and repeating.