13-29
EXTERNAL MEMORY INTERFACE
13.8.6 Example 6: RD1:0 = 11, 16-bit Bus, External EPROM and RAM
In this example, an 80C251SB operates in page mode with a 16-bit external address bus inter-
faced to 64 Kbytes of EPROM and 64 Kbytes of RAM (Figure 13-27). The 80C251SB is config-
ured so that RD# is asserted for addresses
≤
7F:FFFFH, and PSEN# is asserted for addresses
≥
80:0000.
This system is the same as Example 5 (Figure 13-25) except that it operates in page mode. Ac-
cordingly, the two systems have the same memory map (Figure 13-26), and the comments on ad-
dressing external RAM apply here also.
Figure 13-27. Bus Diagram for Example 6: 80C251SB in Page Mode
A4146-01
A7:0
A15:8/D7:0
A15:8
Latch
PSEN#
80C251SB
RD#
WR#
P2
P0
EA#
EPROM
(64 Kbytes)
OE#
D7:0
A15:8
A7:0
CE#
CE#
A15:8
A7;0
RAM
(64 Kbytes)
D7:0
OE#
WE#
Code
Data
Содержание 8XC251SA
Страница 2: ......
Страница 3: ...May 1996 8XC251SA 8XC251SB 8XC251SP 8XC251SQ Embedded Microcontroller User s Manual...
Страница 18: ......
Страница 19: ...1 Guide to This Manual...
Страница 20: ......
Страница 30: ......
Страница 31: ...2 Architectural Overview...
Страница 32: ......
Страница 41: ...3 Address Spaces...
Страница 42: ......
Страница 63: ...4 Device Configuration...
Страница 64: ......
Страница 81: ...5 Programming...
Страница 82: ......
Страница 102: ......
Страница 103: ...6 Interrupt System...
Страница 104: ......
Страница 120: ......
Страница 121: ...7 Input Output Ports...
Страница 122: ......
Страница 132: ......
Страница 133: ...8 Timer Counters and Watchdog Timer...
Страница 134: ......
Страница 153: ...9 Programmable Counter Array...
Страница 154: ......
Страница 170: ......
Страница 171: ...10 Serial I O Port...
Страница 172: ......
Страница 187: ...11 Minimum Hardware Setup...
Страница 188: ......
Страница 197: ...12 Special Operating Modes...
Страница 198: ......
Страница 206: ......
Страница 207: ...13 External Memory Interface...
Страница 208: ......
Страница 239: ...14 Programming and Verifying Nonvolatile Memory...
Страница 240: ......
Страница 250: ......
Страница 251: ...A Instruction Set Reference...
Страница 252: ......
Страница 390: ......
Страница 391: ...B Signal Descriptions...
Страница 392: ......
Страница 400: ......
Страница 401: ...C Registers...
Страница 402: ......
Страница 436: ......
Страница 437: ...Glossary...
Страница 438: ......
Страница 446: ......
Страница 447: ...Index...
Страница 448: ......
Страница 458: ......