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GSSIP Message Format

The GSSIP1GSSIP = GPS STANDARD SERIAL INTERFACE PROTOCOL format includes 3 ICD-GPS-153C messages which are used to support emulation of a SAASM GPS used in a SINCGARS interface. The messages are the Buffer Box (253), Time Transfer (5101), and the Current Status (5040).

The ICD-GPS-153C protocol defines the format of these messages. The Current Status and Time Transfer are sent once per second (1Hz). The Buffer Box is sent once every 6 seconds (1/6 Hz).

The purpose of these three messages is to emulate a SINCGARS interface connection to a SAASM GPS. VersaSync generates these messages emulating the Time and 1PPS transfer behavior of the SINCGARS interface. An external device compatible with the SINCGARS interface can attach to an ASCII Output from VersaSync and receive time and 1PPS as if communicating with and ICD-GPS-153C compatible SAASM GPS.

These commands are emulated only and contain only time information; position and velocity information is zeroed out. No controlled data is included in the messages, hence no SAASM GPS receiver is required.


The ASCII Output supports two configurations for supporting SINCGARS:

A configuration of Time Transfer as Message Format1 and Current Status as Format2 causes the SINCGARS protocol to be emulated and the machine state to be initializated.

  • Format1: Time Transfer (5101)
  • Format2: Current Status (5040)
  • Format3: Buffer Box (253)

A configuration of Current Status as Message Format1 and Time Transfer as Format2 results in broadcasting of the messages Current Status (1Hz), Time Transfer (1Hz), and Buffer Box (1/6Hz) at their default rates.

  • Format1: Current Status (5040)
  • Format2: Time Transfer (5101)
  • Format3: Buffer Box (253)