DS89C420-QCL Datasheet, PDF (74/139 Pages) Maxim Integrated Products – Ultra-High-Speed Flash Microcontroller User’s Guide

Ultra-High-Speed Flash
Microcontroller User’s Guide
PAGE MODE 1 DATA MEMORY TIMING–PAGES 1:0 = 00b (ONE CYCLE)
The first diagram below illustrates execution of back-to-back MOVX instructions from internal flash memory. The default MOVX stretch
setting (MD2:0 = 001b) has been assumed. The total duration of each MOVX instruction is seven system clocks = one system clock
(page-hit memory cycle) + 2 system clocks (page-miss memory cycle) + four system clocks (one stretch cycle). Note that all external
MOVX operations in one-cycle page mode 1 result in page-misses.
The second diagram illustrates execution of the same back-to-back MOVX instructions with a stretch value of 0 (MD2:0 = 000b).
ONE-CYCLE PAGE MODE 1: MOVX (THREE CYCLES) — MOVX (THREE CYCLES)
SYSCLK
ALE
PSEN
WR / _RD
PORT2
PORT0
MOVX
MSB
MOVX#1 LSB Address
MOVX data
MOVX
MSB
MOVX#2 LSB Address
MOVX data
MOVX MOVX
#1 #2
MOVX #1 Data Access
(Page Miss + 1 Stretch Cycle)
INST
MOVX #2 Data Access
(Page Miss + 1 Stretch Cycle)
INST
ONE-CYCLE PAGE MODE 1: MOVX (TWO CYCLES) — MOVX (2 CYCLES)
SYSCLK
ALE
PSEN
WR / _RD
PORT2
PORT0
MOVX MOVX
MSB LSB
MOVX
DATA
MOVX MOVX
MSB LSB
MOVX
DATA
MOVX MOVX
#1 #2
MOVX #1
Data Access
(Page Miss)
INST
MOVX #2
Data Access
(Page Miss)
INSTRUCTIONS
= STRETCH CYCLE
_____________________________________________________________________________________________ 74