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Update comments in abc9_map.v
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Eddie Hung
parent
1dc22607c3
commit
bae3d8705d
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@ -28,12 +28,53 @@
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// ============================================================================
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// The purpose of the following FD* rules are to wrap the flop (which, when
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// called with the `_ABC' macro set captures only its combinatorial
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// behaviour) with:
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// `abc9' requires that complex flops be split into a combinatorial box
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// feeding a simple flop ($_ABC9_FF_).
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// Yosys will automatically analyse the simulation model (described in
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// cells_sim.v) and detach any $_DFF_P_ or $_DFF_N_ cells present in
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// order to extract the combinatorial control logic left behind.
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// Specifically, a simulation model similar to the one below:
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//
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// ++===================================++
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// || Sim model ||
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// || /\/\/\/\ ||
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// D -->>-----< > +------+ ||
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// R -->>-----< Comb. > |$_DFF_| ||
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// CE -->>-----< logic >-----| [NP]_|---+---->>-- Q
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// || +--< > +------+ | ||
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// || | \/\/\/\/ | ||
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// || | | ||
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// || +----------------------------+ ||
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// || ||
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// ++===================================++
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//
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// is transformed into:
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//
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// ++==================++
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// || Comb box ||
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// || ||
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// || /\/\/\/\ ||
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// D -->>-----< > || +------+
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// R -->>-----< Comb. > || |$_ABC_|
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// CE -->>-----< logic >--->>-- $nextQ --| FF_ |--+-->> Q
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// $currQ +-->>-----< > || +------+ |
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// | || \/\/\/\/ || |
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// | || || |
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// | ++==================++ |
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// | |
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// +----------------------------------------------+
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//
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// The purpose of the following FD* rules are to wrap the flop with:
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// (a) a special $__ABC9_FF_ in front of the FD*'s output, indicating to abc9
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// the connectivity of its basic D-Q flop
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// (b) a special TECHMAP_REPLACE_.$currQ wire that will be used for feedback
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// (b) a special _TECHMAP_REPLACE_.$abc9_clock wire to capture its clock
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// domain (used when partitioning the module so that `abc9' only
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// performs sequential synthesis (with reachability analysis) correctly on
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// one domain at a time)
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// (c) a special _TECHMAP_REPLACE_.$abc9_control that captures the control
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// domain (which, combined with this cell type, encodes to `abc9' which
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// flops may be merged together)
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// (d) a special _TECHMAP_REPLACE_.$currQ wire that will be used for feedback
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// into the (combinatorial) FD* cell to facilitate clock-enable behaviour
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module FDRE (output reg Q, input C, CE, D, R);
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parameter [0:0] INIT = 1'b0;
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@ -49,56 +90,11 @@ module FDRE (output reg Q, input C, CE, D, R);
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) _TECHMAP_REPLACE_ (
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.D(D), .Q($nextQ), .C(C), .CE(CE), .R(R)
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);
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// `abc9' requires that complex flops be split into a combinatorial box
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// feeding a simple flop ($_ABC9_FF_).
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// Yosys will automatically analyse the simulation model (described in
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// cells_sim.v) and detach any $_DFF_P_ or $_DFF_N_ cells present in
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// order to extract the combinatorial control logic left behind.
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// Specifically, a simulation model similar to the one below:
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//
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// ++===================================++
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// || Sim model ||
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// || /\/\/\/\ ||
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// D -->>-----< > +------+ ||
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// R -->>-----< Comb. > |$_DFF_| ||
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// CE -->>-----< logic >-----| [NP]_|---+---->>-- Q
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// || +--< > +------+ | ||
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// || | \/\/\/\/ | ||
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// || | | ||
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// || +----------------------------+ ||
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// || ||
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// ++===================================++
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//
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// is transformed into:
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//
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// ++==================++
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// || Comb box ||
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// || ||
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// || /\/\/\/\ ||
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// D -->>-----< > || +------+
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// R -->>-----< Comb. > || |$_ABC_|
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// CE -->>-----< logic >--->>-- $nextQ --| FF_ |--+-->> Q
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// $currQ +-->>-----< > || +------+ |
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// | || \/\/\/\/ || |
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// | || || |
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// | ++==================++ |
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// | |
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// +----------------------------------------------+
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, IS_C_INVERTED};
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// Special signal indicating control domain
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// (which, combined with this cell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, IS_D_INVERTED, R, IS_R_INVERTED};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = Q;
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endmodule
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module FDRE_1 (output reg Q, input C, CE, D, R);
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@ -111,19 +107,9 @@ module FDRE_1 (output reg Q, input C, CE, D, R);
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, 1'b1 /* IS_C_INVERTED */};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, 1'b0 /* IS_D_INVERTED */, R, 1'b0 /* IS_R_INVERTED */};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = Q;
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endmodule
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@ -142,7 +128,7 @@ module FDCE (output reg Q, input C, CE, D, CLR);
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.D(D), .Q($nextQ), .C(C), .CE(CE), .CLR(IS_CLR_INVERTED)
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// ^^^ Note that async
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// control is disabled
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// and captured by
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// here but captured by
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// $__ABC9_ASYNC below
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q($currQ));
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@ -150,19 +136,9 @@ module FDCE (output reg Q, input C, CE, D, CLR);
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// using the $_ABC9_ASYNC box by abc9_map.v
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\$__ABC9_ASYNC abc_async (.A($currQ), .S(CLR ^ IS_CLR_INVERTED), .Y(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, IS_C_INVERTED};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, IS_D_INVERTED, CLR, IS_CLR_INVERTED};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = $currQ;
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endmodule
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module FDCE_1 (output reg Q, input C, CE, D, CLR);
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@ -174,25 +150,15 @@ module FDCE_1 (output reg Q, input C, CE, D, CLR);
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.D(D), .Q($nextQ), .C(C), .CE(CE), .CLR(1'b0)
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// ^^^ Note that async
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// control is disabled
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// and captured by
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// here but captured by
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// $__ABC9_ASYNC below
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q($currQ));
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\$__ABC9_ASYNC abc_async (.A($currQ), .S(CLR), .Y(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, 1'b1 /* IS_C_INVERTED */};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, 1'b0 /* IS_D_INVERTED */, CLR, 1'b0 /* IS_CLR_INVERTED */};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = $currQ;
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endmodule
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@ -211,25 +177,15 @@ module FDPE (output reg Q, input C, CE, D, PRE);
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.D(D), .Q($nextQ), .C(C), .CE(CE), .PRE(IS_PRE_INVERTED)
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// ^^^ Note that async
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// control is disabled
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// and captured by
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// here but captured by
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// $__ABC9_ASYNC below
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q($currQ));
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\$__ABC9_ASYNC abc_async (.A($currQ), .S(PRE ^ IS_PRE_INVERTED), .Y(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, IS_C_INVERTED};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, IS_D_INVERTED, PRE, IS_PRE_INVERTED};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = $currQ;
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endmodule
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module FDPE_1 (output reg Q, input C, CE, D, PRE);
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@ -241,25 +197,15 @@ module FDPE_1 (output reg Q, input C, CE, D, PRE);
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.D(D), .Q($nextQ), .C(C), .CE(CE), .PRE(1'b0)
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// ^^^ Note that async
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// control is disabled
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// and captured by
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// here but captured by
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// $__ABC9_ASYNC below
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q($currQ));
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\$__ABC9_ASYNC abc_async (.A($currQ), .S(PRE), .Y(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, 1'b1 /* IS_C_INVERTED */};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, 1'b0 /* IS_D_INVERTED */, PRE, 1'b0 /* IS_PRE_INVERTED */};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = $currQ;
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endmodule
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@ -279,19 +225,9 @@ module FDSE (output reg Q, input C, CE, D, S);
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, IS_C_INVERTED};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, IS_D_INVERTED, S, IS_S_INVERTED};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = Q;
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endmodule
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module FDSE_1 (output reg Q, input C, CE, D, S);
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@ -304,19 +240,9 @@ module FDSE_1 (output reg Q, input C, CE, D, S);
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);
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\$__ABC9_FF_ abc_dff (.D($nextQ), .Q(Q));
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// Special signal indicating clock domain
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// (used to partition the module so that `abc9' only performs
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// sequential synthesis (reachability analysis) correctly on
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// one domain at a time)
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// Special signals
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wire [1:0] _TECHMAP_REPLACE_.$abc9_clock = {C, 1'b1 /* IS_C_INVERTED */};
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// Special signal indicating control domain
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// (which, combined with this spell type, encodes to `abc9'
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// which flops may be merged together)
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wire [3:0] _TECHMAP_REPLACE_.$abc9_control = {CE, 1'b0 /* IS_D_INVERTED */, S, 1'b0 /* IS_S_INVERTED */};
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// Special signal indicating the current value of the flip-flop
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// In order to achieve clock-enable behaviour, the current value
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// of the sequential output is required which Yosys will
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// connect to the special `$currQ' wire.
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wire _TECHMAP_REPLACE_.$currQ = Q;
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endmodule
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