Altera RapidIO II MegaCore Function Manual de usuario descargar pdf (Pagina 81)

Chapter 4: Functional Description 4–39

Logical Layer Interfaces

August 2014 Altera Corporation RapidIO II MegaCore Function

User Guide

write transaction. In the example, the IP core throttles the incoming transaction for

five clock cycles, because it requires six clock cycles to process each write transaction.

The user logic maintains the values on the

mnt_s_write

mnt_s_writedata,

and

mnt_s_address

signals until one clock cycle after the IP core deasserts the

mnt_s_waitrequest

signal, as required by the Avalon-MM specification. In the

following clock cycle, user logic sends the next write request, which the IP core also

throttles for five clock cycles. The process repeats for an additional two write requests.

The RapidIO II IP core converts these write transactions to RapidIO

MAINTENANCE

request packets. Table 4–17 lists the fields in the corresponding RapidIO packets.

Table 4–17. Maintenance Write Request Transmit Example: RapidIO Packet Fields (Part 1 of 2)

Field Value Comment

ackID

6'h00

Value is written by the Physical layer before the packet is transmitted on the

RapidIO link.

0 The RapidIO II IP core supports only VC0.

CRF

prio[1:0]

2'b00

The IP core assigns to this field the value programmed in the

PRIORITY

field of

the

Tx Maintenance Mapping Window n Control

page 6–36) for the matching address translation window

. Refer to “Defining

the Maintenance Address Translation Windows” on page 4–34 for details.

tt[1:0]

2'b00 The value of 0 indicates 8-bit device IDs.

ftype[3:0]

4'b1000 The value of 8 indicates a Maintenance Class packet.

destinationID[7:0]

The IP core assigns to this field the value programmed in the

DESTINATION_ID

field of the

Tx Maintenance Mapping Window n Control

(Table 6–44 on page 6–36) for the matching address translation window

Refer to “Defining the Maintenance Address Translation Windows” on

page 4–34 for matching details.

sourceID[7:0]

The IP core assigns to this field the value programmed in the

Base_deviceID

field of the

Base Device ID

ttype[3:0]

4’b0001 The value of 1 indicates a

MAINTENANCE

write request.

wrsize[3:0]

4'b1000

The

size

and

wdptr

values encode the maximum size of the payload field. In

MAINTENANCE

transactions, the value of

wrsize

is always 4’b1000, which

decodes to a value of 4 bytes. For encoding details, refer to Table 4-4 in Part 1:

Input/Output Logical Specification of the RapidIO Interconnect Specification,

Revision 2.2.

srcTID[7:0]

The RapidIO II IP core generates the source transaction ID value internally to

track the transaction response. The value depends on the current state of the

RapidIO II IP core when it prepares the RapidIO packet.

config_offset[20:0]

Depends on the value on the

mnt_s_address

bus, and the values programmed

in the

Tx Maintenance Address Translation Window

registers, as

defined in Table 6–41 through Table 6–44. Refer to “Defining the Maintenance

Address Translation Windows” on page 4–34 for the matching and conversion

calculations.

wdptr

The IP core assigns to this field the negation of

mnt_s_address[0]

1 2 ... 76 77 78 79 80 81 82 83 84 85 86 ... 217 218

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