Owner's manual

Table Of Contents
DS785UM1 13-1
Copyright 2007 Cirrus Logic
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Chapter 13
13SDRAM, SyncROM, and SyncFLASH Controller
13.1 Introduction
Note: In the EP9301 and 9302 processors, the common address/data bus is 16-bits wide
and the SDRAM, SyncROM, and SyncFLASH synchronous memory controller
supports 16-bit and 8-bit devices.
Note: In the EP9307, EP9312, and EP9315 processors, the common address/data bus is
programmable to be either 16-bits or 32-bits wide and the SDRAM, SyncROM, and
SyncFLASH synchronous memory controller supports 32-bit , 16-bit, and 8-bit
devices.
The SDRAM controller provides a high speed memory interface to single-data-rate SDRAMs,
Synchronous FLASH, and Synchronous ROMs.
The key features of the SDRAM controller are:
Raster DMA input port for high-bandwidth display refreshing.
Up to four synchronous memory banks that can be independently configured
Special configuration bits for Synchronous ROM operation
Ability to program Synchronous FLASH devices using write and erase commands
Data is transferred between the controller and the synchronous memory device in quad-
word bursts.
Programmable for 16 or 32-bit data bus: EP9307, EP9312, and EP9315 processors only
SDRAM contents are preserved when a “soft” reset is asserted
Power saving synchronous memory clock enable
13.2 Booting from SyncROM or SyncFLASH
During power-on reset, if the values on the processor pins shown in Table CAUTION: select
either a Synchronous ROM device or Synchronous FLASH device to be used for booting up
the processor, a short configuration sequence is activated and completed before the
processor is released from power-on reset. By default, Synchronous Memory Bank 3,
controlled by device configuration register SDRAMDevCfg[3:0], is used for booting.
For a Synchronous ROM device, the configuration sequence writes RAS = 0x2 and CAS =
0x5 to the SDRAMDevCfg[3:0] register and writes RAS = 0x2, CAS = 0x5, and either Burst