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Old 09-17-2003, 03:31 AM
Michael
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Default Multi-Source

hello
I'm trying to implement a PCI bus, and i'm trying to interpret C/BE
for the number of words to be read.. what i have done is, to have one
process that "listens" for C/BE and interprets it, then in another
process, it decrements the count per read.. I get the multi source
error, because I can't modify the same signal in 2 processes.. How
else can I approach this? The following is my code:
counting: process(C_BE, AD)
begin
case DEV_RTYP is
when "0100" =>
count <= "010";
when "0101" =>
count <= "011";
when others =>
end case;
end process counting;

out_logic: process(current_state, DEV_DATA, DEV_ADDR, DEV_RTYP,
DEV_RDY, DEV_GRNT,
FRAME, C_BE, IRDY, TRDY, DEVSEL, AD)
begin
...
case current_state is
...
when "00011" =>
IRDY <= '1';
DRV_RDY <= '1';
DEV_DATA <= AD;
if LAST = '1' then
FRAME <= '0';
else
FRAME <= '1';
end if;
count <= count - 1;
...
end process out_logic;

please help

thank you
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  #2 (permalink)  
Old 09-17-2003, 01:15 PM
Mario Trams
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Default Re: Multi-Source

Michael wrote:

> hello
> I'm trying to implement a PCI bus, and i'm trying to interpret C/BE
> for the number of words to be read.. what i have done is, to have one
> process that "listens" for C/BE and interprets it, then in another
> process, it decrements the count per read.. I get the multi source
> error, because I can't modify the same signal in 2 processes.. How
> else can I approach this? The following is my code:


y <= a when en_a = '1' else (others => 'Z');
y <= b when en_b = '1' else (others => 'Z');
......

Regards,
Mario

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  #3 (permalink)  
Old 09-17-2003, 02:53 PM
Dan RADUT
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Default Re: Multi-Source

[email protected] (Michael) wrote in message news:<[email protected] com>...
Hi:

Try as I suggest below:

> I'm trying to implement a PCI bus, and i'm trying to interpret C/BE
> for the number of words to be read.. what i have done is, to have one
> process that "listens" for C/BE and interprets it, then in another
> process, it decrements the count per read.. I get the multi source
> error, because I can't modify the same signal in 2 processes.. How
> else can I approach this? The following is my code:
> counting: process(C_BE, AD)

-- add current_state to this process sensitivity list, that is change this line
-- of code to:
-- coounting: process(C_BE, AD, current_state)
> begin
> case DEV_RTYP is
> when "0100" =>
> count <= "010";
> when "0101" =>
> count <= "011";
> when others =>

-- here insert this piece of code:
-- if current_state = "00011" then
-- count <= count - 1;
-- else
-- null;
-- end if;
-- then go to the other process and...
> end case;
> end process counting;
>
> out_logic: process(current_state, DEV_DATA, DEV_ADDR, DEV_RTYP,
> DEV_RDY, DEV_GRNT,
> FRAME, C_BE, IRDY, TRDY, DEVSEL, AD)
> begin
> ...
> case current_state is
> ...
> when "00011" =>
> IRDY <= '1';
> DRV_RDY <= '1';
> DEV_DATA <= AD;
> if LAST = '1' then
> FRAME <= '0';
> else
> FRAME <= '1';
> end if;

-- delete (or comment) the statement below: thus you remove the second source
-- of the count driver.
> count <= count - 1;
> ...
> end process out_logic;
>


good luck,

Dan R
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