7-9
INPUT/OUTPUT PORTS
NOTE
Avoid MOV P0 instructions for external memory accesses. These instructions
can corrupt input code bytes at port 0.
External signal ALE (address latch enable) facilitates external address latch capture. The address
byte is valid after the ALE pin drives V
OL
. For write cycles, valid data is written to port 0 just prior
to the write (WR#) pin asserting V
OL
. Data remains valid until WR# is undriven. For read cycles,
data returned from external memory must appear at port 0 before the read (RD#) pin is undriven
(refer to the 8XC251Sx datasheet for exact specifications). Wait states, by definition, affect bus-
timing.
Table 7-2. Instructions for External Data Moves
Bus Width
Instructions
8
MOVX @Ri; MOV @Rm; MOV dir8
16
MOVX @DPTR; MOV @WRj; MOV @WRj+dis; MOV dir16
17
MOV @DRk; MOV @DRk+dis
18
MOV @DRk; MOV @DRk+dis
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: ......