Figure 7-9. Pre-Shifting Routine; Software Design - Sharp LH79524 User Manual

LH79524/LH79525 User's Guide

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.
ADDR_SHIFT
YES
DEVICE
WIDTH = 32?
NO
DEVICE YES
WIDTH = 16?
NO
OUTPUT ADDRESS
ON PINS A[23:0]
RETURN
Figure 7-9.
Pre-shifting Routine
Version 1.0
External Memory Controller
RIGHT SHIFT
ADDRESS ONE BIT
RIGHT SHIFT
ADDRESS ONE BIT
LH79525-113
7-9