8–10
Chapter 8: External Memory Interfaces in the Cyclone III Device Family
Cyclone III Device Family Memory Interfaces Pin Support
In Cyclone III device family, the ×9 mode uses the same
DQ
and
DQS
pins as the ×8
mode, and one additional
DQ
pin that serves as a regular I/O pin in the ×8 mode. The
×18 mode uses the same
DQ
and
DQS
pins as ×16 mode, with two additional
DQ
pins
that serve as regular I/O pins in the ×16 mode. Similarly, the ×36 mode uses the same
DQ
and
DQS
pins as the ×32 mode, with four additional
DQ
pins that serve as regular
I/O pins in the ×32 mode. When not used as
DQ
or
DQS
pins, the memory interface pins
are available as regular I/O pins.
Optional Parity, DM, and Error Correction Coding Pins
Cyclone III device family supports parity in ×9, ×18, and ×36 modes. One parity bit is
available per eight bits of data pins. You can use any of the
DQ
pins for parity in
Cyclone III device family because the parity pins are treated and configured similar to
DQ
pins.
DM pins are only required when writing to DDR2 and DDR SDRAM devices.
QDR II SRAM devices use the BWS# signal to select the byte to be written into
memory. A low signal on the DM or BWS# pin indicates the write is valid. Driving the
DM or BWS# pin high causes the memory to mask the
DQ
signals. Each group of
DQS
and
DQ
signals has one DM pin. Similar to the
DQ
output signals, the DM signals are
clocked by the -90° shifted clock.
In Cyclone III device family, the DM pins are preassigned in the device pinouts. The
Quartus II Fitter treats the
DQ
and DM pins in a
DQS
group equally for placement
purposes. The preassigned
DQ
and DM pins are the preferred pins to use.
Some DDR2 SDRAM and DDR SDRAM devices support error correction coding
(ECC), a method of detecting and automatically correcting errors in data
transmission. In 72-bit DDR2 or DDR SDRAM, there are eight ECC pins and 64 data
pins. Connect the DDR2 and DDR SDRAM ECC pins to a separate
DQS
or
DQ
group in
Cyclone III device family. The memory controller needs additional logic to encode
and decode the ECC data.
Address and Control/Command Pins
The address signals and the control or command signals are typically sent at a single
data rate. You can use any of the user I/O pins on all I/O banks of Cyclone III device
family to generate the address and control or command signals to the memory device.
1
Cyclone III device family does not support QDR II SRAM in the burst length of two.
Memory Clock Pins
In DDR2 and DDR SDRAM memory interfaces, the memory clock signals (CK and
CK#) are used to capture the address signals and the control or command signals.
Similarly, QDR II SRAM devices use the write clocks (K and K#) to capture the
address and command signals. The CK/CK# and K/K# signals are generated to
resemble the write-data strobe using the DDIO registers in Cyclone III device family.
f
For more information about CK/CK# pins placement, refer to the “Pin Connection
Guidelines Tables” section in the
chapter of the
External Memory Interface Handbook.
Cyclone III Device Handbook
Volume 1
July 2012 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
