13-35
INTERFACING WITH EXTERNAL MEMORY
To write single bytes on a 16-bit bus requires separate low-byte and high-byte write signals
(WRL# and WRH#). Figure 13-18 shows a sample circuit that combines WR#, BHE#, and ad-
dress bit 0 (A0) to produce these signals. This additional logic is unnecessary, however. In the
write strobe mode, WRL# and WRH# are available at the device’s external pins.
Figure 13-18. Decoding WRL# and WRH#
The write strobe mode eliminates the need to externally decode high-byte and low-byte write sig-
nals to external 16-bit memory on a 16-bit bus. When the write strobe mode is selected, the
WR#/WRL# pin operates as WRL#, and the BHE#/WRH# pin operates as WRH#. In the 16-bit
bus mode, WRL# is asserted for all low-byte writes (even addresses) and all word writes, and
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 (see Table 13-14).
BHE#
WR#
A0
WRH#
WRL#
A0104-01
Содержание 80C196NU
Страница 1: ...8XC196NP 80C196NU Microcontroller User s Manual...
Страница 2: ...8XC196NP 80C196NU Microcontroller User s Manual August 1995 Order Number 272479 002...
Страница 18: ...1 Guide to This Manual...
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Страница 32: ...2 Architectural Overview...
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Страница 48: ...3 Advanced Math Features...
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Страница 56: ...4 Programming Considerations...
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Страница 72: ...5 Memory Partitions...
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Страница 106: ...6 Standard and PTS Interrupts...
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Страница 144: ...7 I O Ports...
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Страница 166: ...8 Serial I O SIO Port...
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Страница 184: ...9 Pulse width Modulator...
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Страница 196: ...10 Event Processor Array EPA...
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Страница 226: ...11 Minimum Hardware Considerations...
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Страница 240: ...12 Special Operating Modes...
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Страница 256: ...13 Interfacing with External Memory...
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Страница 304: ...A Instruction Set Reference...
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Страница 374: ...B Signal Descriptions...
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Страница 390: ...C Registers...
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Страница 448: ...Glossary...
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Страница 458: ...Index...
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