DS89C420-ENL MAXIM [Maxim Integrated Products], DS89C420-ENL Datasheet - Page 21
DS89C420-ENL
Manufacturer Part Number
DS89C420-ENL
Description
Ultra-High-Speed Microcontroller
Manufacturer
MAXIM [Maxim Integrated Products]
Datasheet
1.DS89C420-ENL.pdf
(58 pages)
- Current page: 21 of 58
- Download datasheet (670Kb)
DS89C420
EXTERNAL MEMORY
The DS89C420 executes external memory cycles for code fetches and read/writes of external program
and data memory. A non-page external memory cycle is four times slower than the internal memory
cycles (i.e., an external memory cycle contains four system clocks)*. However, a page mode external
memory cycle can be completed in 1, 2, or 4 system clocks for a page hit and 2, 4, or 8 system clocks for
a page miss, depending on user selection. The DS89C420 also supports a second page mode operation
with a different external bus structure that provides for fast external code fetches but uses 4 system clock
cycles for data memory access.
*For this reason, although a DS89C420 can be substituted for a ROM-less 8051 device (DS80C310,
C320, etc.), there is no increase in execution speed.
EXTERNAL PROGRAM MEMORY INTERFACE (NON-PAGE MODE)
Figure 3 shows the timing relationship for internal and external code fetches when CD1 and CD0 are set
to 10b, assuming the microcontroller is in non-page mode for external fetches. Note that an external
program fetch takes 4 system clocks, and an internal program fetch requires only 1 system clock.
As illustrated in Figure 3, ALE is deasserted when executing an internal memory fetch. The DS89C420
provides a programmable user option to turn on ALE during internal program memory operation. ALE is
automatically enabled for code fetch externally, independent of the setting of this option.
PSEN is only asserted for external code fetches, and is inactive during internal execution.
21 of 58
Related parts for DS89C420-ENL
Image
Part Number
Description
Manufacturer
Datasheet
Request
R
Part Number:
Description:
IC MCU 50MHZ ULTRA HS 44-PLCC
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU 50MHZ ULTRA HS 40-DIP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU 50MHZ ULTRA HS 44-TQFP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 33MHZ HP 44-TQFP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 25MHZ HP 44-TQFP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 33MHZ HP 40-DIP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 33MHZ HP 40-DIP
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 33MHZ HP 44-PLCC
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 25MHZ HP 44-PLCC
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
IC MCU ULTRA 33MHZ HP 44-PLCC
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
LCC/M/CIRCUITI INTEGRATI MAXIM
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
KIT/E/MAXIM ANALOG ESSENTIALS # COLLECTION OF PLUG-IN EVALUATION MODULES
Manufacturer:
Maxim Integrated Products
Part Number:
Description:
Single +5V, fully integrated, 1.25Gbps laser diode driver.
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
Single +5V, fully integrated, 155Mbps laser diode driver.
Manufacturer:
Maxim Integrated Products
Datasheet:
Part Number:
Description:
VRD11/VRD10, K8 Rev F 2/3/4-Phase PWM Controllers with Integrated Dual MOSFET Drivers
Manufacturer:
Maxim Integrated Products
Datasheet: