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PDF DS2251T Data sheet ( Hoja de datos )

Número de pieza DS2251T
Descripción 128k Soft Microcontroller Module
Fabricantes Dallas Semiconducotr 
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No Preview Available ! DS2251T Hoja de datos, Descripción, Manual

DS2251(T)
128k Soft Microcontroller Module
www.dalsemi.com
FEATURES
8051-compatible microcontroller adapts to its
task
- 32K, 64K, or 128K bytes of nonvolatile
SRAM for program and/or data storage
- In-system programming via on-chip serial
port
- Capable of modifying its own program or
data memory in the end system
- Provides separate Byte-wide bus for
peripherals
- Performs CRC-16 check of NV RAM
memory
High-reliability operation
- Maintains all nonvolatile resources for
over 10 years in the absence of power
- Power-fail reset
- Early Warning Power-fail Interrupt
- Watchdog Timer
- Lithium backed memory remembers
system state
- Precision reference for power monitor
Fully 8051-compatible
- 128 bytes scratchpad RAM
- Two timer/counters
- On-chip serial port
- 32 parallel I/O port pins
Permanently powered real time clock
PIN ASSIGNMENT
72-Pin SIMM
DESCRIPTION
The DS2251T 128k Soft Microcontroller Module is an 8051-compatible microcontroller module based on
nonvolatile RAM technology. It is designed for systems that need large quantities of nonvolatile memory.
Like other members of the Secure Microcontroller family, it provides full compatibility with the 8051
instruction set, timers, serial port, and parallel I/O ports. By using NV RAM instead of ROM, the user can
program, then reprogram the microcontroller while in-system. The application software can even change
its own operation. This allows frequent software upgrades, adaptive programs, customized systems, etc.
In addition, by using NV RAM, the DS2251T is ideal for data logging applications. The powerful real
time clock includes interrupts for time stamp and date. It keeps time to one-hundredth of seconds using its
onboard 32 kHz crystal.
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DS2251T pdf
PIN
16
17
9
29
30
19, 18
20
40
72
54-41
63-56
64
66
67
31
DS2251T
DESCRIPTION
P3.6 WR . General purpose I/O port pin. Also serves as the write strobe for Expanded bus
operation.
P3.7 RD . General purpose I/O port pin. Also serves as the read strobe for Expanded bus
operation.
RST - Active high reset input. A logic 1 applied to this pin will activate a reset state. This
pin is pulled down internally, can be left unconnected if not used. An RC power-on reset
circuit is not needed and is NOT recommended.
PSEN - Program Store Enable. This active low signal is used to enable an external program
memory when using the Expanded bus. It is normally an output and should be unconnected
if not used.
ALE - Address Latch Enable. Used to de-multiplex the multiplexed Expanded
Address/Data bus on Port 0. This pin is normally connected to the clock input on a ‘373
type transparent latch.
XTAL2, XTAL1. Used to connect an external crystal to the internal oscillator. XTAL1 is
the input to an inverting amplifier and XTAL2 is the output.
GND - Logic ground.
VCC - +5V.
BA15 - Monitor test point to reflect the logical value of A15. Not needed for memory
access.
BA13 - 0. Byte-wide Address bus bits 13-0. This bus is combined with the non-multiplexed
data bus (BD7-0) to access onboard NV SRAM and off-board peripherals. Peripheral
decoding is performed using PE3 and PE4 . These are on 16k boundaries, so BA14 or BA15
are not needed. Read/write access is controlled by R/ W . BA13-0 connect directly to
memory mapped peripherals.
BD7 - 0. Byte-wide Data bus bits 7-0. This 8-bit bi-directional bus is combined with the
non-multiplexed address bus (BA14-0) to access on-board NV SRAM and off-board
peripherals.
R/ W - Read/Write. This signal provides the write enable to the SRAMs on the Byte-wide
bus. It is controlled by the memory map and Partition. The blocks selected as Program
(ROM) will be write-protected. This signal is also used for the write enable to off-board
peripherals.
PE3 - Peripheral Enable 3. Accesses data memory between addresses 8000h and BFFFh
when the PES bit is set to a logic 1. PE3 is not lithium backed and can be connected to any
type of peripheral function.
PE4 - Peripheral Enable 4. Accesses data memory between addresses C000h and FFFFh
when the PES bit is set to a logic 1. PE4 is not lithium backed and can be connected to any
type of peripheral function.
PROG - Invokes the Bootstrap loader on a falling edge. This signal should be debounced so
that only one edge is detected. If connected to ground, the micro will enter Bootstrap
loading on power-up. This signal is pulled up internally.
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DS2251T arduino
# PARAMETER
SYMBOL
@ 16 MHz
25 Data Valid after WR High
tWRHDV
26 RD Low to Address Float
tRDLAZ
27 RD or WR High to ALE High
tRDHALH
MIN
7tCLK -90
tCLK -50
tCLK -40
EXPANDED PROGRAM MEMORY READ CYCLE
MAX
0
tCLK +50
DS2251T
UNITS
ns
ns
ns
ns
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