Altera RapidIO II MegaCore Function Uživatelský manuál stáhnout pdf (Strana 83)

Chapter 4: Functional Description 4–41

Logical Layer Interfaces

August 2014 Altera Corporation RapidIO II MegaCore Function

User Guide

User Sending MAINTENANCE Read Requests and Receiving Responses

Table 4–19 lists the Maintenance Avalon-MM interface usage example this section

describes.

Figure 4–18 shows the behavior of the signals for two read transfers on the

Maintenance Avalon-MM slave interface.

In the first active clock cycle of the example, user logic specifies that the active

transaction is a read request, by asserting the

mnt_s_read

signal while specifying the

source address for the read data on the

mnt_s_address

signal. However, the

RapidIO II IP core throttles the incoming transaction by asserting the

mnt_s_writerequest

signal until it is ready to receive the read transaction. In the

example, the IP core throttles the incoming transaction for four clock cycles. The user

logic maintains the values on the

mnt_s_read

and

mnt_s_address

signals until one

clock cycle after the IP core deasserts the

mnt_s_waitrequest

signal. In the following

clock cycle, user logic sends the next read request, which the IP core also throttles for

four clock cycles.

The RapidIO II IP core presents the read responses it receives on the RapidIO link as

read data responses on the Maintenance Avalon-MM slave interface. The IP core

presents the read data responses in the same order it receives the original read

requests, by asserting the

mnt_s_readdatavalid

signal while presenting the data on

the

mnt_s_data

bus.

The RapidIO II IP core converts the read requests to RapidIO transactions. Table 4–20

lists the fields in the corresponding RapidIO transactions.

Table 4–19. Maintenance Interface Usage Example: Sending MAINTENANCE Read Request and

Receiving Response

User Operation Device ID Width Payload Size (Bytes)

Send

MAINTENANCE

read request 16 0

Receive

MAINTENANCE

read response 16 32

Figure 4–18. Read Transfers on the Maintenance Avalon-MM Slave Interface

mnt_s_read

mnt_s_address

mnt_s_readdata

mnt_s_readerror

0x14 0x4C

system clock

mnt_s_readdatavalid

mnt_s_waitrequest

Table 4–20. Maintenance Read 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.

1 2 ... 78 79 80 81 82 83 84 85 86 87 88 ... 217 218

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