Architecture
395
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
12. Program the SDRAM refresh control register (SDRCR). All of the following steps may be done with a
single register write to SDRCR:
(a) Set LPMODEN bit to enable self-refresh. This is necessary for the next two steps.
(b) Set MCLKSTOPEN bit to enable MCLK stopping. This is necessary for the next two steps.
(c) Clear SR_PD bit to select self-refresh. This is necessary for the next two steps.
(d) Program RR refresh rate value to meet the memory data sheet specification.
13. Program the Power and Sleep Controller (PSC) to reset (SyncReset) the DDR2/mDDR memory
controller.
14. Program the Power and Sleep Controller (PSC) to re-enable the DDR2/mDDR memory controller.
15. Clear LPMODEN and MCLKSTOPEN bits in SDRCR to disable self-refresh.
16. Configure the peripheral bus burst priority register (PBBPR) to a value lower than the default value of
FFh. A lower value reduces the likelihood of prolonged command starvation for accesses made from
different master/peripherals to mDDR/DDR2 memory. The optimal value should be determined based
on system considerations; however, a value of 20h or 30h is sufficient for typical applications.
NOTE:
Some memory data sheet timing values such as those programmed into the SDRAM timing
register 1 (SDTIMR1) and SDRAM timing register 2 (SDTIMR2) may need to be relaxed in
order to compensate for signal delays introduced by board layout.
14.2.14 Interrupt Support
The DDR2/mDDR memory controller supports two addressing modes, linear incrementing and cache line
wrap. Upon receipt of an access request for an unsupported addressing mode, the DDR2/mDDR memory
controller generates an interrupt by setting the LT bit in the interrupt raw register (IRR). The DDR2/mDDR
memory controller will then treat the request as a linear incrementing request.
This interrupt is called the line trap interrupt and is the only interrupt the DDR2/mDDR memory controller
supports. It is an active-high interrupt and is enabled by the LTMSET bit in the interrupt mask set register
(IMSR). This interrupt is mapped to the CPU and is multiplexed with RTCINT.
14.2.15 DMA Event Support
The DDR2/mDDR memory controller is a DMA slave peripheral and therefore does not generate DMA
events. Data read and write requests may be made directly by masters and by the DMA.