431 Dual Deque
431 : Dual Deque
- Author: Andrew Dona-Couch
- Description: Dual byte-width double-ended queues
- GitHub repository
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Two independent double-ended queues in one tiny footprint.
How it works
Each deque is an array of flip flops with a pointer to the top. The empty and full status flags for each are directly available on pins. The push and pop inputs as well as data bus lines are multiplexed using the deque select line.
Hold end_select low to operate as a stack. Tie end_select to push to operate
as a queue.
How to test
To push (if full is low):
- Put the data byte on
data_in - Select which deque to push to with
deque_select - Select which end to push to with
end_select - Bring
pushhigh for one cycle
To pop (if empty is low):
- Select which deque to push to with
deque_select - Select which end to push to with
end_select - Bring
pophigh for one cycle
To replace the last element of the deque (if empty is low):
- Select which deque to push to with
deque_select - Select which end to push to with
end_select - Put the new data byte on
data_in - Bring both
pushandpophigh for one cycle
To read the end of the deque:
- Select which deque to push to with
deque_select - Select which end to push to with
end_select - Wait one cycle
- Read end of deque from
data_out
External hardware
You would probably want to connect this to other devices that would find it useful.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | Data In 0 | Data Out 0 | Deque Select |
| 1 | Data In 1 | Data Out 1 | End Select |
| 2 | Data In 2 | Data Out 2 | Push |
| 3 | Data In 3 | Data Out 3 | Pop |
| 4 | Data In 4 | Data Out 4 | Deque 0 Empty |
| 5 | Data In 5 | Data Out 5 | Deque 0 Full |
| 6 | Data In 6 | Data Out 6 | Deque 1 Empty |
| 7 | Data In 7 | Data Out 7 | Deque 1 Full |