DS89C420-QCL Datasheet, PDF (98/139 Pages) Maxim Integrated Products – Ultra-High-Speed Flash Microcontroller User’s Guide

Ultra-High-Speed Flash
Microcontroller User’s Guide
XTAL1
1st
Cycle
2nd
Cycle
ALE
PSEN
RD / WR
Port 0
Inst Inst Inst Inst
MOVX Instruction (Page miss)
3rd
Cycle
4th
Cycle
Port 2
LSB LSB LSB LSB
MOVX
Instruction
Fetch
MSB
Memory Access (Stretch = 4)
ALE
MOVX Instruction (Page hit)
1st 2nd
Cycle Cycle
3rd
Cycle
4th
Cycle
5th
Cycle
PSEN
RD / WR
Port 0
Inst Inst Inst Inst
Port 2
LSB LSB LSB LSB
MOVX
Instruction
Fetch
Figure 10-4. External Program Memory Access (Page Mode 1)
Memory Access (Stretch = 4)
9th
Cycle
Data
Inst Inst
LSB
LSB LSB
9th
Cycle
Data
Inst Inst Inst
LSB
LSB LSB LSB
INTERNAL MEMORY CYCLES
XTAL1
ALE
PSEN
PORT 0
EXT CODE FETCHES
PAGE MISS
PAGE HIT
PAGE HIT
C1
C2
C3
C4
C1
C2
C1
C2
LSB ADD
LSB ADD
LSB ADD
PORT 2
MSB ADD
DATA
DATA
DATA
Figure 10-5. External Program Memory Access (Page Mode 2)
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