.model top
.inputs clk cen ina inb
.outputs outa outb outc outd
.names $false
.names $true
1
.names $undef
.subckt DFFE clk=clk data=ina cen=cen out=ina_n1
.subckt DFF clk=clk data=ina_n1 out=outa
.subckt DFFN clk=clk data=ina_n1 out=outc
.subckt DFFNE clk=clk data=inb cen=ina out=inb_n1
.subckt DFF clk=clk data=inb_n1 out=outb
.subckt DFFN clk=clk data=inb_n1 out=outd
.end