DS89C420 Dallas Semiconducotr, DS89C420 Datasheet - Page 31

• Manufacturer Part Number: DS89C420
• Description: Ultra-High-Speed Microcontroller
• Manufacturer: Dallas Semiconducotr

Figure 9. Page Mode 1, External Data Memory Access (Pages = 01,
Stretch = 1, CD = 10)
Figure 9 illustrates the external data-memory stretch cycle timing relationship when PAGEE = 1 and
PAGES1:PAGES0 = 01. The stretch cycle shown is for a stretch value of 1 and is coincident with a page
miss. Note that the first stretch value does not result in adding four system clocks to the RD / WR control
signals. This is because the first stretch uses one system clock to create additional setup and one system
clock to create additional hold time.
RD / WR
RD / WR
RD / WR
XTAL1
PSEN
Port 0
Port 2
PSEN
Port 0
Port 2
PSEN
Port 0
Port 2
ALE
ALE
ALE
LSB Addr
LSB Addr
LSB Addr
Inst
Inst
Inst
MOVX Inst
Fetch
MOVX Inst
Fetch
LSB Addr
LSB Addr
LSB Addr
MOVX
MOVX
Inst
LSB Addr
MSB Addr
MSB Addr
Inst
MSB Addr
LSB Addr
LSB Addr
Memory Access (Stretch =1)
MOVX
Inst
MOVX Instruction
MOVX Instruction
31 of 59
Memory Access (Stretch =1)
LSB Addr
Inst
Memory Access (Stretch =1)
LSB Addr
LSB Addr
MOVX Instruction
Data
Data
LSB Addr
Data
LSB Addr
LSB Addr
Inst
Inst
LSB Addr
LSB Addr
LSB Addr
Inst
Inst
Inst
LSB Addr
LSB Addr
LSB Addr
Inst
Inst
Inst