Download VPI-II, Data Logger

Generic Point Interface
6.5.
DATALOGGER'S GPI MESSAGES
Commands and responses sent through a GPI port are the same as those typed in
when using the system’s diagnostic menus through the MAC port. However, only
commands and responses stated in this section are supported. Issuing commands other
than those discussed here may cause undesirable results.
Each DataLogger GPI command is composed of a series of ASCII printable characters,
terminated with the ASCII non-printable ETX (end-of-text) character (Control/C or
hexadecimal 0x03). Each command should be preceded by the ASCII non-printable
ENQ character (Control/E or hexadecimal 0x05), the “request for Main Menu”
command.
The communication protocol for transferring DataLogger commands to the GPI is the
text mode of the DataTrain VIII protocol. All commands must therefore be packaged in
DataTrain VIII format:
•
Begin with the text message type identifier (0xAF)
•
Followed by the station address
•
Terminated with a 2-byte checksum (CRC16) and the end-of-message character
(0xA9)
This format is illustrated in Figure 6–1 with a station address of three used for example
purposes only.
AF
03
DL Command or Response Data CRC A9
DT8 Message Terminator
Two Byte CRC
Actual DL inquiry or Response Data
DT8 Station Address
DT8 Message Type (Text)
Figure 6–1. DataTrain VIII Message Format
P2512E, Rev. Mar/08
6–3
Alstom Signaling Inc.