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DDR_D[15:0]
DDR2
memory
controller
DDR_CLK
DDR_CLK
DDR_CS
DDR_CKE
DDR_RAS
DDR_WE
DDR_DQM[1:0]
DDR_CAS
DDR_BA[2:0]
DDR_DQS[1:0]
DDR_A[13:0]
DDR_ZP
50 Ω
DDR_DQGATE0
DDR_DQGATE1
DDR_VREF
Architecture
371
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
14.2.1.2 Clock Configuration
The frequency of 2X_CLK is configured by selecting the appropriate PLL multiplier. The PLL multiplier is
selected by programming registers within PLLC1. The PLLC1 divider ration is fixed at 1. For information
on programming the PLL controllers, see the
Phase-Locked Loop Controller (PLLC)
chapter. For
information on supported clock frequencies, see the
Device Clocking
chapter and your device-specific
data manual.
NOTE:
PLLC1 should be configured and a stable clock present on 2X_CLK before releasing the
DDR2/mDDR memory controller from reset.
14.2.1.3 DDR2/mDDR Memory Controller Internal Clock Domains
There are two clock domains within the DDR2/mDDR memory controller. The two clock domains are
driven by VCLK and a divided-down by 2 version of 2X_CLK called MCLK. The command FIFO, write
FIFO, and read FIFO described in
are all on the VCLK domain. From this, VCLK drives the
interface to the peripheral bus.
The MCLK domain consists of the DDR2/mDDR memory controller state machine and memory-mapped
registers. This clock domain is clocked at the rate of the external DDR2/mDDR memory, 2X_CLK/2.
To conserve power within the DDR2/mDDR memory controller, VCLK, MCLK, and 2X_CLK may be
stopped. See
for proper clock stop procedures.
14.2.2 Signal Descriptions
The DDR2/mDDR memory controller signals are shown in
and described in
Memory Controller Signal Descriptions
. The following features are included:
•
The maximum data bus is 16-bits wide.
•
The address bus is 14-bits wide with an additional three bank address pins.
•
Two differential output clocks driven by internal clock sources.
•
Command signals: Row and column address strobe, write enable strobe, data strobe, and data mask.
•
One chip select signal and one clock enable signal.
Figure 14-3. DDR2/mDDR Memory Controller Signals