Altera DQ (ALTDQ) - Manual (Page 2)

Page 2 Introduction
DQ (ALTDQ) and DQS (ALTDQS) Megafunctions November 2010 Altera Corporation
■ Stratix ®
■ Stratix GX
■ Stratix II
■ Stratix II GX
ALTDQ Megafunction
The ALTDQ megafunction allows you to easily configure the DDR I/O elements in
supported Altera devices for DQ data signal functionality. The ALTDQ megafunction
is a variation of the ALTDDIO_BIDIR megafunction modified to be used with the
ALTDQS megafunction.
The ALTDQ megafunction implements a DDR interface and offers many additional
features, which include:
■ Transmission and reception of data on both edges of the reference clock
■ ddioinclk clock input for the negative-edge input register (available for Stratix II
devices only)
■ Active high asynchronous clear and clock-enable control inputs
■ Registered or unregistered output-enable input
ALTDQS Megafunction
The ALTDQS megafunction allows you to easily configure the I/O elements of the
data strobe (DQS) in supported Altera devices.
You typically use the ALTDQS megafunction used with the ALTDQ megafunction
which provides the following features:
■ A group of DQS pins used to strobe the read and write data in external DDR
memory interfaces using a common DLL to phase shift the read strobe
■ Implementing one DLL and a number of user-specified DQS pins (the maximum
number of DQS supported by a DLL is also dependent on the device side)
■ Clocks generated for the DQ negative-edge input registers from the DQSn pins
that is the dqddioinclk[] signal (available for Stratix II devices only)
■ Delay buffer setting output option
■ Frequency settings of DQS inputs and system reference clock
■ Active-high asynchronous clear and clock-enable control inputs
■ Registered or unregistered output-enable input
■ DQS outputs configurable as open drain mode
■ Speed setting of the DQS and delay buffers as either low or high (available for
Stratix II devices only)