DS2250(T)

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INSTRUCTION SET

The DS2250(T) executes an instruction set which is object code-compatible with the industry standard

8051 microcontroller. As a result, software development packages which have been written for the 8051

are compatible with the DS2250(T), including cross-assemblers, high-level language compilers, and

debugging tools. Note that the DS2250(T) is functionally identical to the DS5000(T) except for package

and the 64k memory option.

A complete description for the DS2250(T) instruction set is available in the User’s Guide section of the

Secure Microcontroller Data Book.

MEMORY ORGANIZATION

Figure 2 illustrates the address spaces which are accessed by the DS2250(T). As illustrated in the figure,

separate address spaces exist for program and data memory. Since the basic addressing capability of the

machine is 16 bits, a maximum of 64 kbytes of program memory and 64 kbytes of data memory can be

accessed by the DS2250(T) CPU. The 8- or 32-kbyte RAM area inside of the DS2250(T) can be used to

contain both program and data memory. A second 32k RAM is available for data only.

The Real Time Clock (RTC) in the DS2250(T) is reached in the memory map by setting a SFR bit. The

MCON.2 bit (ECE2) is used to select an alternate data memory map. While ECE2=1, all MOVXs will be

routed to this alternate memory map. The real time clock is a serial device that resides in this area. A full

description of the RTC access and example software is given in the User’s Guide section of the Secure

Microcontroller Data Book.