Supported Use Cases
400
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
Configuring SDRAM Refresh Control Register (SDRCR)
The SDRAM refresh control register (SDRCR) configures the DDR2/mDDR memory controller to meet the
refresh requirements of the attached memory device. SDRCR also allows the DDR2/mDDR memory
controller to enter and exit self refresh and enable and disable the MCLK stopping. In this example, we
assume that the DDR2/mDDR memory controller is not is in self-refresh mode or power-down mode and
that MCLK stopping is disabled.
The RR field in SDRCR is defined as the rate at which the attached memory device is refreshed in
DDR2/mDDR cycles. The value of this field may be calculated using the following equation:
RR = DDR2/mDDR clock frequency × DDR2/mDDR memory refresh period
displays the DDR2-400 refresh rate specification.
Table 14-16. DDR2 Memory Refresh Specification
Symbol
Description
Value
t
REF
Average Periodic Refresh Interval
7.8
μ
s
Therefore, the following results assuming 150 MHz DDR2/mDDR clock frequency.
RR = 150 MHz × 7.8
μ
s = 1170
Therefore, RR = 1170 = 492h.
shows the resulting SDRCR configuration.
Table 14-17. SDRCR Configuration
Field
Value
Function Selection
LPMODEN
0
DDR2/mDDR memory controller is not in power-down mode.
MCLKSTOP_EN
0
MCLK stopping is disabled.
SR_PD
0
Leave a default value.
RR
492h
Set to 492h DDR2 clock cycles to meet the DDR2/mDDR memory refresh rate requirement.