RapidIO: The Next Generation Communication Fabric For Embedded Application

8.6. FIELD PLACEMENT AND DEFINITION

This section contains information on the additional physical layer bit fields and control symbols required to implement the flow control, error management, and other specified system functions in the parallel RapidIO interface.

8.6.1. Flow Control Fields Format

The fields used to control packet flow in the system are described below (Table 8.8).

Figure 8.9 shows the format for the physical layer fields for packets. In order to pad packets to the 16-bit boundary there are three reserved bits in a packet's physical layer fields. These bits are assigned to logic 0 when generated and ignored when received. The figure also shows how the physical layer fields are prefixed to the combined transport and logical layer packet.

The unshaded fields are the physical layer fields defined by the physical layer specifica-tion. The shaded fields are the bits associated with the combined transport and logical transaction definitions. The first transport and logical field shown is the two bit tt field described in Chapter 6. The second field is the four bit format type (ftype) defined in Chapters 4, 5, 11 and 12. The third combined field is the remainder of the transport and logical packet. This size and contents of these fields will vary depending on the transaction.

Table 8.8. Fields that control packet flow

Field	Description
S	0b0 RapidIO request or response packet 0b1 Physical layer control symbol
S_bar	Inverse of S-bit for redundancy (odd parity bit)
ackID	Acknowledge ...