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15-25
INTERFACING WITH EXTERNAL MEMORY
15.5.2 Write Strobe Mode
The write strobe mode eliminates the need to externally decode high- and low-byte writes to an
external 16-bit RAM or flash device in 16-bit bus mode. When the write strobe mode is selected,
the microcontroller generates WRL# and WRH# instead of WR# and BHE#. WRL# is asserted
for all low byte writes (even addresses) and all word writes. WRH# is asserted for all high byte
writes (odd addresses) and all word writes. In the 8-bit bus mode, WRH# and WRL# are asserted
for both even and odd addresses. Figure 15-14 shows write strobe mode timing.
Figure 15-14. Write Strobe Mode
ALE
WRL#
WRH#
AD15:0
Valid
Address Data Out
16-bit Bus Cycle
ALE
WRL# and WRH#
AD7:0
AD15:8 Address High
Address Low Data Out
8-bit Bus Cycle
Valid
A3089-01