prjxray/fuzzers/011-clb-ffconfig

clb-ffconfig Fuzzer

Documents FF configuration.

Note Vivado GUI is misleading in some cases where it shows configuration per FF, but its actually per SLICE

Primitive pin map

Element	CE	CK	D	SR	Q
FDRE	CE	C	D	R	Q
FDPE	CE	C	D	PRE	Q
FDSE	CE	C	D	S	Q
FDCE	CE	C	D	CLR	Q
LDPE	GE	G	D	PRE	Q
LDCE	GE	G	D	CLR	Q

Primitive bit map

Prim	FFSYNC	LATCH	ZRST
FDPE
FDSE	X
FDRE	X		X
FDCE			X
LDCE		X	X
LDPE		X

FFSYNC

Configures whether a storage element is synchronous or asynchronous.

Scope: entire site (not individual FFs)

FFSYNC	Reset	Applicable prims
0	Synchronous	FDPE, FDCE, LDCE, LDPE
1	Asynchronous	FDSE, FDRE

LATCH

Configures latch vs FF behavior for the CLB

LATCH	Description	Primitives
0	All storage elements in the CLB are FF's	FDPE, FDSE, FDRE, FDCE
1	LUT6 storage elements are latches (LDCE or LDPE). LUT5 storage elements cannot be used	LDCE, LDPE

N*FF.ZRST

Configures stored value when reset is asserted

Prim	ZRST	On reset
FDRE, FDCE, and LDCE	0	1
FDRE, FDCE, and LDCE	1	0
FDPE, FDSE, and LDPE	0	0
FDPE, FDSE, and LDPE	1	1

N*FF.ZINI

Sets GSR FF or latch value

LATCH	ZINI	Set to
FF	0	1
FF	1	0
LATCH	0	0
LATCH	1	1

CEUSEDMUX

Configures ability to drive clock enable (CE) or always enable clock

CEUSEDMUX	Description
0	always on (CE=1)
1	controlled (CE=mywire)

SRUSEDMUX

Configures ability to reset FF after GSR

SRUSEDMUX	Description
0	never reset (R=0)
1	controlled (R=mywire)

TODO: how used when SR?

CLKINV

Configures whether to invert the clock going into a slice.

Scope: entire site (not individual FFs)

LATCH	CLKINV	Description
FF	0	normal clock
FF	1	invert clock
LATCH	0	invert clock
LATCH	1	normal clock