46 lines
1.0 KiB
OCaml
46 lines
1.0 KiB
OCaml
(**
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* Copyright (c) 2016, Fabien Freling
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* All rights reserved.
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*
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* This source code is licensed under the BSD 2-clause license found in the
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* LICENSE file at the top level directory of this source tree.
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*)
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let frequence = 4194304
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type t = {
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clock_rate : int;
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period : int;
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mutable enabled : bool;
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mutable cycles_left : int;
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}
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let create clock_rate enabled =
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let period = frequence / clock_rate in
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{
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clock_rate;
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period;
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enabled;
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cycles_left = period;
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}
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(** TIMA - Timer counter *)
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let create_tima tac =
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let enabled = Bit.is_set tac 2 in
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let clock_select = tac land 0b00000011 in
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let clock_rate = match clock_select with
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| 0 -> 4096
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| 1 -> 262144
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| 2 -> 65536
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| 3 -> 16384
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| _ -> failwith "Unreachable clock rate code."
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in
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create clock_rate enabled
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let update timer cycles =
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let remain = timer.cycles_left - cycles in
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let should_inc = remain <= 0 in
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if should_inc then
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timer.cycles_left <- remain + timer.period;
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should_inc
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