ARM NIC-301 User Manual

ARM DDI 0397G

2-15

ID031010

The AMBA Network Interconnect converts FIXED bursts to one or more INCR1 or INCRn 
bursts depending on the downsize ratio. Table 2-6 shows how the network converts FIXED 
bursts when it downsizes them.

The AMBA Network Interconnect optimizes unaligned fixed bursts. If an unaligned input fixed 
burst maps onto a single output beat, then the output is a fixed burst of the optimal size.

You can configure the downsizer function to have a programmable bit named 

bypass_merge

. If 

bypass_merge

 is asserted, the network does not perform any packing of beats to match the 

optimum SIZE, up to the output data width SIZE.

An aligned input burst means that the address is aligned to the input data width word boundary 
after the network aligns it to the transfer size. An unaligned input burst means that the address 
is not aligned to the input data width word boundary, even after the network aligns it to the 
transfer size.

If a transaction passes through, this means that the downsize function does not change the input 
transaction size and type.

 •

If an exclusive transaction is split into multiple transactions at the output of the downsizer, 
the exclusive flag is removed and the master never receives an EXOKAY response. 
Response priority is the same as for the upsize function. See Upsizing data width function 
on page 2-12.

•

In the following example, the input data width is 128-bit and the output data width is 
64-bit unless otherwise stated.

You can configure the acceptance capability to 1-32 read transactions and 1-32 write 
transactions. The maximum issuing capability is (ratio x acceptance capability +1).

If you configure the network as a clock frequency crossing bridge, then a FIFO function is also 
configured.

 You can configure the buffering for multiple outstanding transactions even if you are using a 1:1 
clocking ratio.

FIXED1

INCR2

FIXED2

INCR2 + INCR2 + ...