From d8d40aa1fed08739c8e99caf07a75179d9143ff5 Mon Sep 17 00:00:00 2001 From: "Wesley W. Terpstra" <w.terpstra@gsi.de> Date: Fri, 4 Nov 2011 15:40:04 +0100 Subject: [PATCH] wb_crossbar: Document the timing and area costs of the crossbar. Signed-off-by: Tomasz Wlostowski <tomasz.wlostowski@cern.ch> --- modules/wishbone/wb_crossbar/xwb_crossbar.vhd | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/modules/wishbone/wb_crossbar/xwb_crossbar.vhd b/modules/wishbone/wb_crossbar/xwb_crossbar.vhd index 021ed762..17dbe342 100644 --- a/modules/wishbone/wb_crossbar/xwb_crossbar.vhd +++ b/modules/wishbone/wb_crossbar/xwb_crossbar.vhd @@ -23,8 +23,17 @@ -- slave simultaneously, the lowest numbered master is granted access. -- -- The implementation of this crossbar locks a master to a slave so long as --- CYC_O is held high. If the master tries to address outside the slave's --- address range, ERR_I will be raised. +-- CYC_O is held high. +-- +-- Synthesis/timing relevant facts: +-- (m)asters, (s)laves, masked (a)ddress bits +-- +-- Area required = O(ms log(ma)) +-- Arbitration depth = O(log(msa)) +-- Master->Slave depth = O(log(m)) +-- Slave->Master depth = O(log(s)) +-- +-- If g_registered = false, arbitration depth is added to M->S and S->M. -- ------------------------------------------------------------------------------- -- Copyright (c) 2011 GSI / Wesley W. Terpstra -- GitLab