Latency meter

Latency meter is used to measure the duration of a specific event.

Key features

Measures the number of ticks between the start and the end of a given event
Multiple parallel events can be measured
Zero latency events can be measured (start and end occurs at the same time)

Component port and generics description

ENTITY LATENCY_METER IS

Generics

Generic	Type	Default	Description
DATA_WIDTH	integer	UNDEFINED	Tick counter width (defines max. latency)
MAX_PARALEL_EVENTS	integer	1	Defines max. number of parallel events that can be measured
DEVICE	string	“ULTRASCALE”

Ports

Port	Type	Mode	Description
CLK	std_logic	in
RST	std_logic	in
START_EVENT	std_logic	in
END_EVENT	std_logic	in
LATENCY_VLD	std_logic	out
LATENCY	std_logic_vector(DATA_WIDTH - 1 downto 0)	out
FIFO_FULL	std_logic	out	Signals that no more paralel events can be curently measured
FIFO_ITEMS	std_logic_vector(max(log2(MAX_PARALEL_EVENTS), 1) downto 0)	out	Number of paralel latencies in FIFO

Instance template

latency_meter_i : entity work.LATENCY_METER
generic map (
    DATA_WIDTH              => DATA_WIDTH,
    MAX_PARALEL_EVENTS      => MAX_PARALEL_EVENTS,
    DEVICE                  => DEVICE
)
port map (
    CLK                     => CLK,
    RST                     => RST,
    START_EVENT             => start_event,
    END_EVENT               => end_event,
    LATENCY_VLD             => latency_vld,
    LATENCY                 => latency
);