DS89C420-ENG Maxim Integrated Products, DS89C420-ENG Datasheet - Page 31

• Manufacturer Part Number: DS89C420-ENG
• Description: IC MCU ULTRA 25MHZ HP 44-TQFP
• Manufacturer: Maxim Integrated Products
• Series: 89Cr

Specifications of DS89C420-ENG

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: EBI/EMI, SIO, UART/USART
• Peripherals: Power-Fail Reset, WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

Figure 12. Page Mode 2, External Code Fetch Cycle (CD1:CD0 = 10)
STRETCH EXTERNAL DATA MEMORY CYCLE IN PAGE MODE
The DS89C420 allows software to adjust the speed of external data memory access by stretching the memory bus
cycle in page mode operation just like non-page mode operation. The following tables summarize the stretch
values and their effects on the external MOVX-memory bus cycle and the control signals’ pulse width in terms of
the number of oscillator clocks. A stretch machine cycle always contains four system clocks, independent of the
logic value of the page mode select bits.
Table 7. Page Mode 1, Data Memory Cycle Stretch Values (Pages1:Pages0 = 00)
Table 8. Page Mode 1, Data Memory Cycle Stretch Values (Pages1:Pages0 = 01)
XTAL1
MD2:MD0
MD2:MD0
PSEN
Port 0
Port 2
ALE
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
Internal Memory Cycles
STRETCH
CYCLES
STRETCH
CYCLES
10
0
1
2
3
7
8
9
10
0
1
2
3
7
8
9
4X/ 2X , CD1,
4X/ 2X , CD1,
CD0 = 100
CD0 = 100
0.25
0.75
1.75
2.75
3.75
4.75
5.75
6.75
0.25
0.75
1.75
2.75
3.75
4.75
5.75
6.75
RD/WR PULSE WIDTH (IN NUMBER OF OSCILLATOR CLOCKS)
RD / WR PULSE WIDTH (IN NUMBER OF OSCILLATOR CLOCKS)
C1
31 of 47
MSB Add
4X/ 2X , CD1,
4X/ 2X , CD1,
CD0 = 000
C2
CD0 = 000
Page Miss
11.5
13.5
11.5
13.5
0.5
1.5
3.5
5.5
7.5
9.5
0.5
1.5
3.5
5.5
7.5
9.5
LSB Add
C3
Ext Code Fetches
C4
Data
4X/ 2X , CD1,
4X/ 2X , CD1,
CD0 = X10
CD0 = X10
C1
11
15
19
23
27
11
15
19
23
27
Page Hit
1
3
7
1
3
7
LSB Add
C2
Data
C1 C2
Page Hit
4X/ 2X , CD1,
4X/ 2X , CD1,
CD0 = X11
CD0 = X11
11,264
15,360
19,456
23,552
27,648
11,264
15,360
19,456
23,552
27,648
1024
3072
7168
1024
3072
7168
LSB Add
Data