Altera RapidIO II MegaCore Function User Manual
Page 82
4–40
Chapter 4: Functional Description
Logical Layer Interfaces
RapidIO II MegaCore Function
August 2014
Altera Corporation
User Guide
User Receiving MAINTENANCE Write Requests
Table 4–18
lists the Maintenance Avalon-MM interface usage example this section
describes.
The RapidIO II IP core generates write transfers on the Maintenance Avalon-MM
master interface in response to Type 8 MAINTENANCE Write request packets on the
RapidIO link with the following properties:
■
ttype
has the value of 4'b0001, indicating a MAINTENANCE Write request
■
config_offset
has a value that indicates an address outside the range of the
RapidIO II IP core internal register set
Figure 4–17
shows the signal relationships when the RapidIO II IP core presents a
sequence of four write transfers on the Maintenance Avalon-MM master interface.
In the first active clock cycle, the RapidIO II IP core indicates the start of a write
transfer by asserting the usr_mnt_write signal. Simultaneously, the IP core presents
the target address on the usr_mnt_address address bus and the data on the
usr_mnt_writedata
data bus.
In this example, user logic does not assert the usr_mnt_waitrequest signal. However,
when user logic asserts the usr_mnt_waitrequest signal during a write transfer, the IP
core maintains the address and data values on the buses until at least one clock cycle
after user logic deasserts the usr_mnt_waitrequest signal. User logic can use the
usr_mnt_waitrequest
signal to throttle requests on this interface until it is ready to
process them.
hop_count
The IP core assigns to this field the value programmed in the HOP_COUNT field
of the Tx Maintenance Mapping Window n Control register (
) for the matching address translation window n. Refer to
“Defining the Maintenance Address Translation Windows” on page 4–34
for
matching details.
payload[63:0]
The IP core assigns the value of mnt_s_writedata[31:0] to the appropriate
half of this field.
Table 4–17. Maintenance Write Request Transmit Example: RapidIO Packet Fields (Part 2 of 2)
Field
Value
Comment
Table 4–18. Maintenance Interface Usage Example: Receiving MAINTENANCE Write Request
User Operation
Device ID Width
Payload Size (Bytes)
Receive MAINTENANCE write request
8
32
Figure 4–17. Write Transfers on the Maintenance Avalon-MM Master Interface
4
8
C
10
ACACACAC
5C5C5C5C
BEEFBEEF
FACEFACE
usr_mnt_write
usr_mnt_writedata
usr_mnt_address
usr_mnt_waitrequest
system clock