Address Decode - 1.0 English

SmartConnect (PG247)

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1.0 English

The SmartConnect core must determine which MI is the target of each transaction by decoding the address of each AW and AR channel transfer received at an SI. This address decode involves only those upper order address bits needed to distinguish between MIs, and ignores lower-order bits that might be used to distinguish locations within the connected slave device.

The entire address value received from the SI is presented to the MI and made available to the slave device (up to the width of the address signal port of the connected slave). It is visible to any connected monitors, even though the high-order address bits are typically not reused by the slave device.

In some cases, there may be multiple, possibly disjointed, address ranges that define when a single slave device is accessed. The address decode logic in the SmartConnect core includes the multiple ranges that determine the selection of each MI.

Whenever a transaction address received on the SI does not match any of the ranges being decoded by the SmartConnect, the transaction is trapped and handled by a decode error module within the core. The core generates a protocol-compliant response back to the originating master with the decode error (DECERR) response code. The offending transaction is not seen by any connected slave.


IMPORTANT:   There must be no overlap among all address ranges across all MI. These rules are enforced by the tools.

Each SI maintains an address map table containing only those address segments configured for the connected master device in the IP Integrator Address Editor.

When all address segments associates with an MI (connected slave) are omitted (unmapped) from a master’s address space, SmartConnect prevents that master from propagating any transactions to that MI. If a subset (aperture) of a slave’s address segment is mapped to a master’s address space, then only transactions with addresses that fall within the mapped aperture are permitted to propagate to the MI; attempts to access excluded portions of address segments will result in DECERR responses.

SmartConnect performs no address re-mapping. The address segment(s) corresponding to each MI are seen the same way by all SIs that can access the MI (flat address space). Masters with an address width less than the full address width spanned by all accessible slaves, can only access those address segments mapped at the low end of the address space.