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Bus Combiner Module

The VHDL code used to synthesize the logic for the bus combiner address decode GAL is shown below:
-----------------------------------------------------------------------------
-- DACS : Distributed Audio Control System
--
-- Copyright (C) 1997 Stephen Scott Richardson
-----------------------------------------------------------------------------
--   File: buscomb.vhd
--   Date: 03.13.97
-- Target: Atmel ATF16V8B
-----------------------------------------------------------------------------
-- Bus combiner pbus address decoding GAL
--
-- pbus addx    function          dir (from uC)
-- ==================================================
-- 0x30         latch ena         out
-----------------------------------------------------------------------------

ENTITY buscomb_decode IS
	PORT (
		addx_in         :  IN bit_vector (6 DOWNTO 0);
		nlatch_in	:  IN bit;		
		nread_write_in	:  IN bit;
		relay_ena_out   :  OUT bit;
                nsense_out      :  OUT bit
             );

-- force part and pinout
ATTRIBUTE part_name of buscomb_decode:entity is "C16V8";
ATTRIBUTE pin_numbers of buscomb_decode:entity is
	  "nread_write_in:1 nlatch_in:2 addx_in(0):3 addx_in(1):4
           addx_in(2):5 addx_in(3):6 addx_in(4):7 addx_in(5):8
           addx_in(6):9 nsense_out:12 relay_ena_out:13";

END buscomb_decode;


ARCHITECTURE behavior OF buscomb_decode IS
BEGIN
	PROCESS (nlatch_in, addx_in, nread_write_in)
	BEGIN
		IF nlatch_in = '0' AND nread_write_in = '1'
		   AND addx_in = "0110000" THEN
			
			-- pbus 0x30

			nsense_out <= '0';     -- pbus nsense ACTIVE
			relay_ena_out <= '1';  -- data latch ena ACTIVE

		ELSE

			-- not active

			nsense_out <= '1';     -- pbus nsense ACTIVE
			relay_ena_out <= '0';  -- data latch ena INACTIVE

		END IF;
	END PROCESS;
END behavior;
The pinout for the bus combiner decode GAL is shown below:
                     C16V8A
                 ________________
 nread_write_in =| 1|        |20|* not used       
      nlatch_in =| 2|        |19|* not used       
      addx_in_0 =| 3|        |18|* not used       
      addx_in_1 =| 4|        |17|* not used       
      addx_in_2 =| 5|        |16|* not used       
      addx_in_3 =| 6|        |15|* not used       
      addx_in_4 =| 7|        |14|* not used       
      addx_in_5 =| 8|        |13|= relay_ena_out  
      addx_in_6 =| 9|        |12|= nsense_out     
       not used *|10|        |11|* not used       
                 ________________


Steve Richardson 2000-07-06
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