Altera ALTDLL - Manual (Page 26)

3–8 Chapter 3: Parameter Settings
ALTDQ_DQS Parameter Editor
ALTDLL and ALTDQ_DQS Megafunctions User Guide © February 2012 Altera Corporation
■ Reset/Config Ports
Table 3–4 describes the options available on the DQS IN page. This page allows you
to configure the DQS input path. For more information about the DQS input path,
refer to
“DQS Input Path” on page 4–6 .
Table 3–4. Options on DQS IN Page (Part 1 of 3)
Parameter Name Legal Value
Clear Box
Parameter Name Description
Enable DQS Input
Path —
USE_DQS_INPUT_PATH
Instantiates the DQS input path.
Enable DQS Input
Path —
USE_DQS_INPUT_PATH
Instantiates the DQS input path.
Delay chain
usage:
Enable dynamic
delay chain
— USE_DQS_INPUT_
DELAY_CHAIN
Enables <IO> _INPUT_DELAY_CHAIN (D1) on the
DQS input path. If you turn on this parameter,
DQS_DELAY_CHAIN block in the path is disabled. D1
is a run-time adjustable delay chain.
To configure delay chains dynamically, refer to “Delay
Chains” on page 4–15 .
Delay chain
usage:
Enable
dqs_delay_chain
— USE_DQS_DELAY_
CHAIN
Enables DQS_DELAY_CHAIN block. The DQS delay
chain is a DLL-controlled delay chain used to phase shift
the DQS read clock.
Enable DQS
busout delay
chain — USE_DQSBUSOUT_
DELAY_CHAIN
Enables DQSBUSOUT_DELAY_CHAIN (Da). This
busout delay chain fine-tunes the outputs of
DQS_DELAY_CHAIN block so that the DQS strobe
timing matches the DQS enable signal. The DQS strobe
has 15 steppable delays, with each step having 50 ps of
delay. Da is a run-time adjustable delay chain.
Enable DQS
enable block — USE_DQS_ENABLE Enables DQS_ENABLE block. This block grounds the
DQS input strobe when the strobe goes to high
impedance state (Z) after a DDR read postamble.
Enable DQS
enable control
block — USE_DQS_ENABLE_
CTRL
Enables DQS_ENABLE_CTRL block that controls a
DQS enable circuitry.
You must determine an efficient working
resync_postamble_clk clock phase which clocks
this block to ensure smooth data transfer. The
ALTDQ_DQS megafunction cannot determine the phase
for the data transfer.
Use round trip delay (RTD) analysis or create a custom
data training circuitry to write and read back a training
pattern to and from the memory device and then
dynamically adjust the PLL’s resyncronization clock
phase to find an efficient working phase.
Even though this block controls the DQS enable signal,
the megafunction does not consider the necessary
timing for this signal. Refer to the external memory
interface requirements for the necessary timing.