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PIA6821: always read the input for port A

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Feedback of the output can be applied externally
This commit is contained in:
Gyorgy Szombathelyi 2022-10-18 12:51:20 +02:00
parent 34cc39fc87
commit efa81db65b
1 changed files with 9 additions and 5 deletions
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14
common/IO/pia6821.vhd
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@ -31,6 +31,14 @@
-- Set output to low level when in data is in input mode
-- (to avoid infered latch warning)
--
-- 18 October 2022 0.0.3 Slingshot
-- Run through VHDLFormatter.
-- Port A always read the input data.
-- Feedback of output can be applied externally if required, as:
-- pa_i <= (pa_o and pa_oe) or (pa_input and not pa_oe);
-- In some applications, the input is stronger than the output,
-- and the feedback is suppressed.
--
--===========================================================================----
--
-- Memory Map
@ -134,11 +142,7 @@ BEGIN
data_out(count) <= porta_ddr(count);
porta_read <= '0';
ELSE
IF porta_ddr(count) = '1' THEN
data_out(count) <= porta_data(count);
ELSE
data_out(count) <= pa_i(count);
END IF;
data_out(count) <= pa_i(count);
porta_read <= cs;
END IF;
END LOOP;