The decoder is used to perform centralised address decoding, which improves the portability of peripherals by making them independent of the system memory map.
General outline for address decoding:
The central decoder is used to provide the select signal selX, for each of the subordinates on the bus
A subordinate must only sample the address and control signals and selX when ready is high (current transfer is completing)
The minimum address space that can be allocated to a single subordinate is 1kB
The manager will be designed such that they will not perform incrementing transfers over 1kb
Default Subordinate Note
In case an SoC does not contain a completely filled memory map (which is very likely early on with us), a default subordinate must be implemented to provide a response when any of the non-existent address locations are accessed
Non-sequential or sequential transfers: Respond error
Idle or busy transfers: Zero-wait state okay response
This functionality will be implemented as part of the decoder
The decoder is used to perform centralised address decoding, which improves the portability of peripherals by making them independent of the system memory map.
General outline for address decoding:
The central decoder is used to provide the select signal
selX, for each of the subordinates on the busA subordinate must only sample the address and control signals and
selXwhenreadyis high (current transfer is completing)The minimum address space that can be allocated to a single subordinate is 1kB
The manager will be designed such that they will not perform incrementing transfers over 1kb
Default Subordinate Note
In case an SoC does not contain a completely filled memory map (which is very likely early on with us), a default subordinate must be implemented to provide a response when any of the non-existent address locations are accessed