User guide

Programmer’s Reference

4.2.2 Memory characteristics

Some memory access characteristics, for example chip select polarity and memory

width, are set by the CONFIGDATA signals. Changing these values might be required,

for example, if you are booting from expansion memory. The signal states are

determined by the SYS_CFGDATAx registers. These registers contain configuration

data to be applied to HDATAM2 pins of the ARM926EJ-S PXP Development Chip

when nPBSDCRECONFIG is asserted by pressing the DEV CHIP RECONFIG

pushbutton. See Configuration from the DEV CHIP RECONFIG pushbutton on

page 3-9 for details of the CONFIGDATA signals.

The values in the SYS_CFGDATAx registers retain their value during the ARM926EJ-S

PXP Development Chip reconfiguration. The DEV CHIP RECONFIG pushbutton can

therefore be used to test different configuration options without resetting the system.

See Configuration registers SYS_CFGDATAx on page 4-25 for details of the power-on

default values.

See also the ARM Multiport Memory Controller (GL175) Technical Reference Manual

and the ARM PrimeCell Static Memory Controller (PL093) Technical Reference

Manual for detailed information on the memory controllers.