ARM NIC-301 2.3 Operation

Functional Description

ID031010 Non-Confidential

2.3 Operation

This section describes how the AMBA Network Interconnect operates and contains the

following subsections:

•Upsizing data width function

•Downsizing data width function on page 2-14

•FIFO and clocking function on page 2-15

•Arbitration on page 2-17

•Cyclic Dependency Avoidance Schemes (CDAS) on page2-17

•Lock support on page 2-18

•TrustZone technology and security on page2-19

•Remap on page 2-21.

2.3.1 Upsizing data width function

The upsizer function can expand the data width by the following ratios:

•1:2

•1:4

•1:8.

Upsizing only packs write data for write or read transactions that are cacheable. This section

describes the packing rules for different burst types and acceptance capabilities, and the

following definitions apply:

• an aligned input burst means that the address is aligned to the output data width word

boundary, after the network aligns it to the size of the transfer

• an unaligned input burst means that the network does not align the address to the output

data width word boundary, even after it aligns it to the size of the transfer

• if a transaction passes through, this means that the upsize function does not change the

input transaction size and type.

Note

• If the network splits input exclusive transactions into more than one output bus

transaction, it removes the exclusive information from the multiple transactions it creates.

• If multiple responses from created transactions are combined into one response, then the

order of priority is:

— DECERR is the highest priority

— SLVERR is the next highest priority

— OKAY is the lowest priority.

In the examples in this section, the input data width is 64-bit, and the output data width is

128-bit, unless otherwise stated. This section describes:

•INCR bursts on page 2-13

•WRAP bursts on page 2-13

•Fixed bursts on page 2-13

•Bypass merge on page2-13

•Acceptance capability on page 2-14.