Altera RapidIO II MegaCore Function - Manual (Page 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.
VC 0 The RapidIO II IP core supports only VC0.