Altera ALTDLL - Manual (Page 67)

4–31 Chapter 4: Functional Description
ALTDLL Megafunction Ports
ALTDLL and ALTDQ_DQS Megafunctions User Guide © February 2012 Altera Corporation
ALTDLL Megafunction Ports
This section describes the ports of the ALTDLL megafunction.
Table 4–9 lists the input ports for the ALTDLL megafunction.
Table 4–9. ALTDLL Megafunction Input Ports
Port Name
Optional/
Required Default Description
dll_aload Optional GND Asynchronous load signal for the DLL counter. When dll_aload is
HIGH , the counter is asynchronously loaded with the initial delay setting
of 16 in low-frequency mode (when the parameter
DELAY_BUFFER_MODE is set to LOW ), or 32 in high-frequency mode
(when the parameter DELAY_BUFFER_MODE is set to HIGH ).
dll_clk Required GND DLL reference clock that matches the frequency of the DQS clock used to
determine the delay for the phase shift. Feed this input by an input pin or
a PLL output. This input must match the polarity of its source and cannot
be inverted.
dll_offset_ctrl
_a_addnsub
Optional V
CC
Addition/subtraction control port for DLL_OFFSET_CTRL_A block.
This port controls whether the delay-offset setting A is added or
subtracted. Ignore this input if the
DLL_OFFSET_CTRL_A_USE_OFFSET parameter is set to FALSE .
If the input is V
CC
, the offset is added; if it is GND , the offset is
subtracted.
dll_offset_ctrl
_a_offset[5..0]
Optional 0 This is the offset input setting for DLL_OFFSET_CTRL_A block. This
is a Gray-coded offset added or subtracted from the current value of the
DLL's delay setting to get the
dll_offset_ctrl_a_offsetctrlout result. Ignore this input
if the DLL_OFFSET_CTRL_A_USE_OFFSET parameter is set to
FALSE . The offset is limited to a minimum value of 0 and a maximum
value of 63 in low-frequency mode, and a maximum value of 31 in
high-frequency mode.
dll_offset_ctrl
_b_addnsub
Optional V
CC
This is the addition/subtraction control port for
DLL_OFFSET_CTRL_B block. This port controls whether the
delay-offset setting B is added or subtracted. Ignore this input if the
DLL_OFFSET_CTRL_B_USE_OFFSET parameter is set to FALSE .
If the input is V
CC
, the offset is added; if it is GND , the offset is
subtracted. This input defaults to V
CC
.
dll_offset_ctrl
_b_offset[5..0]
Optional 0 This is the offset input setting for DLL_OFFSET_CTRL_B block. This
is a Gray-coded offset added or subtracted from the current value of the
DLL's delay setting to get the
dll_offset_ctrl_b_offsetctrlout result. Ignore this input
if the DLL_OFFSET_CTRL_B_USE_OFFSET parameter is set to
FALSE . The offset is limited to a minimum value of 0 and a maximum
value of 63 in low-frequency mode, and a maximum value of 31 in
high-frequency mode.