LH79524/LH79525 User’s Guide
External Memory Controller
Version 1.0
7-9
7.2.3 Software Design
For the bulk of software designs, the automatic address shifting is completely transparent
and no software considerations are needed. However, in instances where software must
control the signal on a specific address pin, the design must account for any address shifting.
7.2.3.1 Simple Shifting Subroutine
If the application requires specific signals on specific address lines, it may be necessary
to pre-shift the address before executing a Read or Write. When addressing 16- or 32-bit
wide devices, a subroutine based on the flow chart in Figure 7-9 handles the necessary
pre-shifting. ‘Device Width’ can be determined by reading the SCONFIGx:MW field.
Figure 7-9.
Pre-shifting Routine
LH79525-113
DEVICE
WIDTH = 32?
ADDR_SHIFT
YES
YES
NO
NO
OUTPUT ADDRESS
ON PINS A[23:0]
RIGHT SHIFT
ADDRESS ONE BIT
DEVICE
WIDTH = 16?
RETURN
RIGHT SHIFT
ADDRESS ONE BIT