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VME64x core
Commit 0a826669 authored by Tristan Gingold's avatar Tristan Gingold
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vme_bus: add comments, simplify berr generation.

parent 56ee00ac
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Showing with 44 additions and 13 deletions
hdl/vme64x-core/rtl/VME_bus.vhd
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......@@ -372,6 +372,9 @@ begin
-- so if VME_IACK_n_i is asserted the FSM is in IDLE state.
-- The VME_IACK_n_i signal is asserted by the Interrupt handler
-- during all the Interrupt cycle.
-- VITA-1 Rule 2.11
-- Slaves MUST NOT respond to DTB cycles when IACK* is low.
if VME_AS_n_i = '0' and VME_IACK_n_i = '1' then
-- if AS falling edge --> start access
s_mainFSMstate <= REFORMAT_ADDRESS;
......@@ -447,6 +450,9 @@ begin
-- this state is necessary indeed the VME master can assert the
-- DS lines not at the same time
VME_DTACK_OE_o <= '1';
-- VITA-1 Rule 2.53a
-- During all read cycles [...], the responding slave MUST OT
-- drive the D[] lines until DSA* goes low.
VME_DATA_DIR_o <= VME_WRITE_n_i;
VME_ADDR_DIR_o <= (s_is_d64) and VME_WRITE_n_i;
s_dataPhase <= s_dataPhase;
......@@ -494,15 +500,34 @@ begin
end case;
end if;
if s_transferType = SINGLE or s_transferType = BLT then
-- VITA-1 Rule 2.6
-- A Slave MUST NOT respond with a falling edge on DTACK* during
-- an unaligned transfer cycle, if it does not have UAT
-- capability.
case s_transferType is
when SINGLE | BLT =>
if s_LWORDlatched_n = '0' and s_ADDRlatched(1) = '1' then
-- unaligned.
s_mainFSMstate <= WAIT_END;
else
s_mainFSMstate <= MEMORY_REQ;
s_memReq <= '1';
elsif s_transferType = MBLT and s_dataPhase = '0' then
end if;
when MBLT =>
if s_dataPhase = '0' then
if s_ADDRlatched(2 downto 1) /= "00" then
-- Unaligned
s_mainFSMstate <= WAIT_END;
else
s_mainFSMstate <= DTACK_LOW;
elsif s_transferType = MBLT and s_dataPhase = '1' then
end if;
else
s_mainFSMstate <= MEMORY_REQ;
s_memReq <= '1';
end if;
when others =>
s_mainFSMstate <= WAIT_END;
end case;
when MEMORY_REQ =>
-- To request the memory CR/CSR or WB memory it is sufficient to
......@@ -548,6 +573,9 @@ begin
s_transferActive <= '1';
s_mainFSMstate <= DTACK_LOW;
-- VITA-1 Rule 2.54a
-- During all read cycles, the responding Slave MUST NOT drive
-- DTACK* low before it drives D[].
if s_transferType = MBLT then
VME_ADDR_o <= s_locDataOutSwap(63 downto 33);
VME_LWORD_n_o <= s_locDataOutSwap(32);
......@@ -575,12 +603,16 @@ begin
s_BERR_out <= '1';
end if;
-- VITA-1 Rule 2.57
-- Once the responding Slave has driven DTACK* or BERR* low, it
-- MUST NOT release them or drive DTACK* high until it detects
-- both DS0* and DS1* high.
if VME_DS_n_i = "11" then
VME_DATA_DIR_o <= '0';
case s_transferType is
when SINGLE =>
-- Cycle should be finished, but allow another access at
-- the same address.
-- the same address (RMW).
s_mainFSMstate <= WAIT_FOR_DS;
when BLT =>
s_mainFSMstate <= INCREMENT_ADDR;
......@@ -699,8 +731,7 @@ begin
if rst_i = '1' then
s_BERRcondition <= '0';
elsif
((s_transferType = error or s_wberr1 = '1') and s_transferActive = '1') or
(s_addressingType = AM_Error) or
(s_wberr1 = '1' and s_transferActive = '1') or
(s_is_d64 = '1' and g_WB_DATA_WIDTH = 32)
then
s_BERRcondition <= '1';
......
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