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[/] [common_components/] [trunk/] [common_switch.vhd] - Rev 4
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------------------------------------------------------------------------------- -- -- Copyright 2020 -- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/> -- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands -- -- Licensed under the Apache License, Version 2.0 (the "License"); -- you may not use this file except in compliance with the License. -- You may obtain a copy of the License at -- -- http://www.apache.org/licenses/LICENSE-2.0 -- -- Unless required by applicable law or agreed to in writing, software -- distributed under the License is distributed on an "AS IS" BASIS, -- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -- See the License for the specific language governing permissions and -- limitations under the License. -- ------------------------------------------------------------------------------- -- Purpose : Switch output high or low -- Description: -- . The output goes high when switch_high='1' and low when switch_low='1'. -- . If g_or_high is true then the output follows the switch_high immediately, -- else it goes high in the next clk cycle. -- . If g_and_low is true then the output follows the switch_low immediately, -- else it goes low in the next clk cycle. -- The g_priority_lo defines which input has priority when switch_high and -- switch_low are active simultaneously. LIBRARY ieee; USE ieee.std_logic_1164.ALL; ENTITY common_switch IS GENERIC ( g_rst_level : STD_LOGIC := '0'; -- Defines the output level at reset. g_priority_lo : BOOLEAN := TRUE; -- When TRUE then input switch_low has priority, else switch_high. Don't care when switch_high and switch_low are pulses that do not occur simultaneously. g_or_high : BOOLEAN := FALSE; -- When TRUE and priority hi then the registered switch_level is OR-ed with the input switch_high to get out_level, else out_level is the registered switch_level g_and_low : BOOLEAN := FALSE -- When TRUE and priority lo then the registered switch_level is AND-ed with the input switch_low to get out_level, else out_level is the registered switch_level ); PORT ( rst : IN STD_LOGIC; clk : IN STD_LOGIC; clken : IN STD_LOGIC := '1'; switch_high : IN STD_LOGIC; -- A pulse on switch_high makes the out_level go high switch_low : IN STD_LOGIC; -- A pulse on switch_low makes the out_level go low out_level : OUT STD_LOGIC ); END; ARCHITECTURE rtl OF common_switch IS SIGNAL switch_level : STD_LOGIC := g_rst_level; SIGNAL nxt_switch_level : STD_LOGIC; BEGIN gen_wire : IF g_or_high=FALSE AND g_and_low=FALSE GENERATE out_level <= switch_level; END GENERATE; gen_or : IF g_or_high=TRUE AND g_and_low=FALSE GENERATE out_level <= switch_level OR switch_high; END GENERATE; gen_and : IF g_or_high=FALSE AND g_and_low=TRUE GENERATE out_level <= switch_level AND (NOT switch_low); END GENERATE; gen_or_and : IF g_or_high=TRUE AND g_and_low=TRUE GENERATE out_level <= (switch_level OR switch_high) AND (NOT switch_low); END GENERATE; p_reg : PROCESS(rst, clk) BEGIN IF rst='1' THEN switch_level <= g_rst_level; ELSIF rising_edge(clk) THEN IF clken='1' THEN switch_level <= nxt_switch_level; END IF; END IF; END PROCESS; p_switch_level : PROCESS(switch_level, switch_low, switch_high) BEGIN nxt_switch_level <= switch_level; IF g_priority_lo=TRUE THEN IF switch_low='1' THEN nxt_switch_level <= '0'; ELSIF switch_high='1' THEN nxt_switch_level <= '1'; END IF; ELSE IF switch_high='1' THEN nxt_switch_level <= '1'; ELSIF switch_low='1' THEN nxt_switch_level <= '0'; END IF; END IF; END PROCESS; END rtl;