Texas Instruments TMS320C645x manual 4x RapidIO Packet Data Stream Streaming-Write Class

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SRIO Functional Description

Figure 6. 1x/4x RapidIO Packet Data Stream (Streaming-Write Class)

n*64+80

PHY	TRA	LOG	TRA	LOG	PHY
10	2	4	16	n*64+32	16

acklD	rsv	prio	tt	ftype	destID	sourcelD	address	rsrv	xamsbs	double-word	double-word	...	double-word		double-word	CRC
5	3	2	2	4	8	8	29	1	2	64	64	(n-4)*64	64	64		16
														n*64+96

PHY =

TRA = Transport

LOG

	PHY	TRA		LOG	TRA	LOG	PHY	LOG	PHY
10		2	4		16	9 * 6 4 + 32	16	(n-9)*64	16

acklD rsv prio tt ftype destiD sourcelD address rsrv xamsbs double-word double-word

... double-word

double-word

CRC double-word

double-word 1

...

double-word

double-word CRC

5 3 2 2 4 8 8 29 1 2 64 64 5*64 64 64 16 64 64 (n-13)*64 64 64 16

Note: Figure 6 assumes that addresses are 32-bit and device IDs are 8-bit.

The device ID, being an 8-bit field, will address up to 256 nodes in the system. If 16-bit addresses were used, the system could accommodate up to 64k nodes.

The data stream includes a Cyclic Redundancy Code (CRC) field to ensure the data was correctly received. The CRC value protects the entire packet except the ackID and one bit of the reserved PHY field. The peripheral checks the CRC automatically in hardware. If the CRC is correct, a Packet-Accepted control symbol is sent by the receiving device. If the CRC is incorrect, a Packet-Not-Accepted control symbol is sent so that transmission may be retried.

2.1.2.3Control Symbols

Control symbols are physical layer message elements used to manage link maintenance, packet delimiting, packet acknowledgment, error reporting, and error recovery. All transmitted data packets are delimited by start-of-packet and end-of-packet delimiters. SRIO control symbols are 24 bits long and are protected by their own CRC. Control symbols provide two functions: stype0 symbols convey the status of the port transmitting the symbol, and stype1 symbols are requests to the receiving port or transmission delimiters. They have the following format, which is detailed in section 3 of the RapidIO LP-Serial specification.

Figure 7. Serial RapidIO Control Symbol Format

Delimiter	1st		2nd			3rd
SC	stype0	Parameter0	parameter1	stype1	cmd		CRC
8	3	5	5	3	3	5

Control symbols are delimited by special characters at the beginning of the symbol. If the control symbol contains a packet delimiter(start-of-packet, end-of-packet, etc.), the special character PD (K28.3) is used. If the control symbol does not contain a packet delimiter, the special character SC (K28.0) is used. This use of special characters provides an early warning of the contents of the control symbol. The CRC does not protect the special characters, but an illegal or invalid character is recognized and flagged as Packet-Not-Accepted. Since control symbols are known length, they do not need end delimiters.

22 Serial RapidIO (SRIO) SPRU976 –March 2006

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