Altera RapidIO II MegaCore Function - Manual (Page 71)

Chapter 4: Functional Description 4–29
Logical Layer Interfaces
August 2014 Altera Corporation RapidIO II MegaCore Function
User Guide
In read requests, if ios_rd_wr_burstcount has a value greater than 1, the only valid
value for ios_rd_wr_byteenable is the value of 16’xFFFF.
Table 4–11 lists the encoding
in the packet header fields of a RapidIO read or write request packet when
ios_rd_wr_burstcount
has a value greater than 1.
For write requests, if ios_rd_wr_burstcount has a value greater than 1, the value of
ios_rd_wr_byteenable
can be different in the first, intermediate, and final clock cycles
of the same request. In all intermediate clock cycles (when ios_rd_wr_burstcount has
a value greater than 2), ios_rd_wr_byteenable must have the value of 16’xFFFF.
Table 4–12 lists the allowed Avalon-MM ios_rd_wr_burstcount and initial and final
clock cycle ios_rd_wr_byteenable value combinations if the value of
ios_rd_wr_burstcount
is greater than 1, and their encoding in the packet header
fields of a RapidIO write request packet.
Table 4–11. I/O Logical Layer Slave Read Request Size Encoding II
Avalon-MM Signal Values (1) RapidIO Header Field Values
burstcount (2)
(5'dx,
128-bit units)
byteenable
(16'hxxxx)
wdptr
(1'bx)
rdsize (2)
(4'bxxxx)
address[0]
(rio_addr[3])
2 FFFF 0 1100 0
3 FFFF 1 1100 0
4 FFFF 1 1100 0
5 FFFF 0 1101 0
6 FFFF 0 1101 0
7 FFFF 1 1101 0
8 FFFF 1 1101 0
9 FFFF 0 1110 0
10 FFFF 0 1110 0
11 FFFF 1 1110 0
12 FFFF 1 1110 0
13 FFFF 0 1111 0
14 FFFF 0 1111 0
15 FFFF 1 1111 0
16 FFFF 1 1111 0
Notes to Table 4–11 :
(1) The I/O Logical layer slave module does not handle byteenable values and byteenable-burstcount combinations
that the Avalon-MM interface does not allow. In case of an invalid byteenable or burstcount value, the RapidIO II
IP core asserts the ios_rd_wr_readresponse signal when it asserts the ios_rd_wr_readdatavalid signal, and sets
the INVALID_READ_BYTEENABLE bit or the INVALID_READ_BURSTCOUNT bit (or both) of the I/O Slave
Interrupt
register ( Table 6–60 on page 6–40 ) if this interrupt is enabled in the I/O Slave Interrupt Enable
register ( Table 6–61 on page 6–41 ).
(2) For read transfers, the read size of the request packet is rounded up to the next supported size, but only the number
of words corresponding to the requested read burst size is returned.