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Message
From: Richard Herveille<richard@h...>
Date: Thu Apr 12 09:11:16 CEST 2007
Subject: [oc] Wishbone spec clarification
> STB can be considered a transfer-valid signal
And of course if you qualify it with per-slave address-decode logic, it
becomes a chip-select.
[rih] True, which is why simple slaves really don't need CYC_I as they
should only qualify STB, however all cores I have seen so far (including
mine) use both CYC_I and STB_I.
Typical ACK_o generation is then like this: ACK_O = CYC_I & STB_I;
If an external address decoder is used, it should validate the address based
on CYC_I. In that case the generated STB_O signals (i.e. chip-selects) are
already validated against CYC_I.
The slave's CYC_I inputs can then be tied to '1'.
Richard
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