RapidIO: The Next Generation Communication Fabric For Embedded Application

7.2. CONTROL SYMBOLS

This section discusses the RapidIO serial physical layer control symbols. Control symbols are the message elements used by ports connected by a serial link to manage all aspects of the serial link operation.

Control symbols (Figure 7.4) can carry two functions, one encoded in the stype0 field and one encoded in the stype1 field. The functions encoded in stype0 are 'status' functions that convey status about the port transmitting the control symbol. The functions encoded in stype1 are either requests to the receiving port or transmission delimiters. The fields para-meter0 and parameter1 are used by the functions encoded in the stype0 field. The cmd field is a modifier for the functions encoded in the stype1 field.

Figure 7.4. Control symbol format

A control symbol carrying one function is referred to by the name of the function it carries. A control symbol carrying two functions may be referred to by the name of either function that it carries. For example, a control symbol with stype0 set to packet-accepted and stype1 set to NOP is referred to a packet-accepted control symbol. A control symbol with stype0 set to packet-accepted and stype1 set to restart-from-retry is referred to as either a packet-accepted control symbol or a restart-from-retry control symbol, depending on which name is appropriate for the context.

Control symbols are specified with the ability ...