Attribute

Allowed Settings and Description

DESKEW_ADJUST

Controls the clock delay alignment between the FPGA clock input pin and the

DCM output clocks.

SYSTEM_SYNCHRONOUS: Default. All devices clocked by a common, system-

wide clock source.

SOURCE_SYNCHRONOUS: Clock is provided by the data source, i.e., source-

synchronous applications.

Do not use this setting to phase shift DCM clock outputs. Instead, use the CLK

and PHASE_SHIFT constraints to achieve accurate phase shifting.

DESKEW_ADJUST has no effect for cascaded DCMs, DCMs using external

feedback, or DCMs where the clock source does not come from a global clock

input routed through the BUFIO2.

STARTUP_WAIT

Controls whether the FPGA configuration signal DONE waits for the DCM to

assert its LOCKED signal before going High. In the starting configuration

sequence, GTS must be deasserted for the DCM to lock.

FALSE: Default. DONE is asserted at the end of configuration without waiting

for the DCM to assert LOCKED.

TRUE: The DONE signal does not transition High until the LOCKED signal

transitions High on the associated DCM. STARTUP_WAIT does not prevent

LOCKED from transitioning High. The FPGA startup sequence must also be

modified to insert a LCK_CYCLE (lock) cycle before the postponed cycle. The

DONE cycle or the GWE cycle are typical choices.

When more than one DCM is configured with STARTUP_WAIT = TRUE, the

FPGA waits until all DCMs are LOCKED. The FPGA waits for all DCMs and

PLLs to be locked when LCK_CYCLE is set without STARTUP_WAIT.

CLKIN_DIVIDE_BY_2

Optionally divides in half the CLKIN before entering the DCM block. In some

applications, CLKIN_DIVIDE_BY_2 reduces the input clock frequency to

acceptable limits.

FALSE: Default. CLKIN input directly feeds the DCM.

TRUE: Divides CLKIN frequency in half and provides roughly a 50% duty cycle

clock before entering the DCM. Helps high frequency clocks meet the DCM input

clock frequency or duty cycle requirements. Divides the clock frequency in half

when determining operating frequency modes and calculating phase shift limits.

LOC

Specifies the physical location of the DCM.

Port

Direction

Description

Indication of M and D programming completeness.

PROGDONE

Output

0: No programming operation of M and D is active, the programming is in progress, or

RST has been asserted.

1: Requested programming is complete. Next PROGCLK operation can commence.

Serial data input to supply information for the programming of M and/or D values of

PROGDATA

Input

the DCM. During programming, the value shifted in will be M –1 or D –1 and will begin

with the LSB. This input must be applied synchronous to the PROGCLK input.

Indication of whether the programming of M and D values is enabled or not.

PROGEN

Input

0: Programming of CLKFX_MULTIPLY and CLKFX_DIVIDE is disabled.

1: Programming of CLKFX_MULTIPLY and CLKFX_DIVIDE is enabled.

Clock input for the programming of M and D values.

PROGCLK

Input

When using a global clock buffer, only the upper eight BUFGMUXs can drive

PROGCLK: BUFGMUX_X2Y1, BUFGMUX_X2Y2, BUFGMUX_X2Y3,

BUFGMUX_X2Y4, BUFGMUX_X3Y5, BUFGMUX_X3Y6, BUFGMUX_X3Y7, and

BUFGMUX_X3Y8.

Attribute

Allowed Settings and Description

CLKFX_MULTIPLY

Defines the multiplication factor for the frequency of the CLKFX and CLKFX180 outputs.

Used in conjunction with the CLKFX_DIVIDE attribute. Allowable values for

CLKFX_MULTIPLY include integers ranging from 2 to 256. Default value is 4.

CLKFX_MULTIPLY

FCLKFX = FCLKIN--------------------------------------------------------CLKFX_DIVIDE

CLKFX_DIVIDE

Defines the division factor for the frequency of the CLKFX and CLKFX180 outputs. Used

in conjunction with the CLKFX_MULTIPLY attribute. Allowable values for

CLKFX_DIVIDE include integers ranging from 1 to 256. Default value is 1.

CLKFX_MULTIPLY

FCLKFX = FCLKIN--------------------------------------------------------CLKFX_DIVIDE

For proper locking with input frequencies below 52 MHz,

FCLKIN

CLKFX_DIVIDE < 0.500--------------------------MHz