.model top
.inputs clk cen ina inb
.outputs outa outb outc outd
.names $false
.names $true
1
.names $undef
.subckt DFF clk=clk data=ina out=outa
.param test_param "PARAM_TEST"
.attr test_attr "ATTR_TEST"
.subckt DFF clk=clk data=inb out=outb
.param test_param "PARAM_TEST"
.attr test_attr "ATTR_TEST"
.end