Motorola MVME2400 Series Wartungshandbuch PDF herunterladen (Seite 263)

Software Considerations

http://www.mcg.mot.com/literature 3-77

Initializing SDRAM Related Control Registers

In order to establish proper SDRAM operation, software must configure

control register bits in Hawk that affect each SDRAM block’s speed, size,

base address, and enable. The SDRAM speed attributes are the same for all

blocks and are controlled by one 32-bit register. The size, base address and

enable can be different for each block and are controlled in individual 8-

bit registers.

SDRAM Speed Attributes

The SDRAM speed attributes come up from power-up reset initialized to

the slowest settings that Hawk is capable of. This allows SDRAM accesses

to be performed before the SDRAM speed attributes are known. An

example of a need for this is when software requires some working

memory that it can use while gathering and evaluating SDRAM device

data from serial EEPROM’s. Once software knows the SDRAM speed

parameters for all blocks, it should discontinue accessing SDRAM for at

least one refresh period before and after it programs the SDRAM speed

attribute bits.

SDRAM Size

The SDRAM size control bits come up from power-up reset cleared to

zero. Once software has determined the correct size for an SDRAM block,

it should set the block’s size bits to match. The value programmed into the

size bits tells the Hawk how big the block is (for map decoding), and how

to translate that block’s 60x addresses to SDRAM addresses.

Programming a block’s size to non-zero also allows it to participate in

scrubbing if scrubbing is enabled.

After software programs the size bits, it should wait for a refresh to happen

before beginning to access SDRAM.

I2C EEPROMs

Most of the information needed to program the SDRAM speed attributes

and size is provided by EEPROM devices that are connected to Hawk’s

I2C bus. The EEPROM devices contain data in a specific format called

Serial Presence Detect (SPD).

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Motorola MVME2400 Series Wartungshandbuch Seite 263