- 8-bit 8051-compatible microcontroller:
- 8051 instruction set
- 32 parallel I/O port pins
- 128-bytes scratchpad RAM
- Two 16-bit timer / counters
- 1 UART
- Reliability enhancements:
- >10 years data retention (with appropriate battery and RAM)
- Early warning power-fail interrupt
- Power-fail reset
- Precision watchdog timer
- Lithium-backed memory
- Ease of use and adaptability:
- 32, 64, or 128kbytes nonvolatile SRAM for program and/or data storage
- On-chip serial port for software downloaded in end system
- Partitioned code and data segments
- Nonmultiplexed bytewide address/data bus for memory access
- ROM-based Serial Bootstrap Loader for in-system reprogramming
- Permanently powered real-time clock
- Operating ranges:
- 16MHz system clock speed (max)
- 0°C to 70°C
The DS2251T provides the benefits of NV RAM without using I/O resources. Between 32 kbytes and 128 kbytes of onboard NV RAM are available. A non-multiplexed Byte-wide address and data bus is used for memory access. This bus, which is available at the connector, can perform all memory access and also provide decoded chip enables for off-board memory mapped peripherals. This leaves the 32 I/O port pins free for application use.
The DS2251T provides high-reliability operation in portable systems or systems with unreliable power. These features include the ability to save the operating state, Power- fail Reset, Power-fail Interrupt, and Watchdog Timer. All nonvolatile memory and resources are maintained for over 10 years at room temperature in the absence of power.
A user loads programs into the DS2251T via its on-chip serial Bootstrap loader. This function supervises the loading of software into NV RAM, validates it, then becomes transparent to the user. Software is stored in onboard CMOS SRAM. Using its internal Partitioning, the DS2251T can divide a common RAM into user-selectable program and data segments. This Partition can be selected at program loading time, but can be modified anytime later. The microprocessor will decode memory access to the SRAM, access memory via its Byte-wide bus and write-protect the memory portion designated as program (ROM).
Operating information is contained in the Secure Microcontroller User's Guide. This data sheet provides ordering information, pinout, and electrical specifications.