Motorola MVME2400 Series Manuel de service télécharger pdf (Page 262)

3-76 Computer Group Literature Center Web Site

System Memory Controller (SMC)

Software Considerations

This section contains information that will be useful in programming a

system that uses the Hawk.

Programming ROM/Flash Devices

Those who program devices to be controlled by the Hawk should make

note of the address mapping that is shown in Table 3-7 and in Table 3-8.

For example, when using 8-bit devices, the code will be split so that every

other 4-byte segment goes in each device.

Writing to the Control Registers

Software should not change control register bits that affect SDRAM

operation while SDRAM is being accessed. Because of pipelining,

software should always make sure that the two accesses before and after

the updating of critical bits are not SDRAM accesses. A possible scenario

for trouble would be to execute code out of SDRAM while updating the

critical SDRAM control register bits. The preferred method is to be

executing code out of ROM/Flash and avoiding SDRAM accesses while

updating these bits.

Some registers have additional requirements for writing. For more

information refer to the register sections in this chapter titled “SDRAM

Enable and Size Register (Blocks A,B,C,D)”, “SDRAM Base Address

E,F,G,H)”, “SDRAM Base Address Register (Blocks E/F/G/H)”, and

“SDRAM Speed Attributes Register.”

Since software has no way of controlling refresh/scrub accesses to

SDRAM, the hardware is designed so that updating control bits

coincidentally with refreshes is not a problem.

As with SDRAM control bits, software should not change control bits that

affect ROM/Flash while the affected Block is being accessed. This

generally means that the ROM/Flash size, base address, enable, write

enable, etc. are changed only while executing initially in the reset vector

area ($FFF00000 - $FFFFFFFF).

1 2 ... 257 258 259 260 261 262 263 264 265 266 267 ... 353 354

Pas de commentaire

Motorola MVME2400 Series Manuel de service Page 262