DS2250_1 Datasheet, PDF (5/19 Pages) Dallas Semiconductor – Soft Microcontroller Module

DS2250(T)
PIN
DESCRIPTION
4, 6, 8, 10, P0.0–P0.7. General purpose I/O Port 0. This port is open–drain and can not drive a logic 1.
12, 14, 16, 18 It requires external pull–ups. Port 0 is also the multiplexed Expanded Address/Data bus.
When used in this mode, it does not require pull–ups.
2
V_CC + – 5 volts.
INSTRUCTION SET
The DS2250(T) executes an instruction set which is ob-
ject 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–as-
semblers, high–level language compilers, and debug-
ging tools. Note that the DS2250(T) is functionally iden-
tical 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 ac-
cessed 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 ac-
cessed by the DS2250(T) CPU. The 8K or 32K byte
RAM area inside of the DS2250(T) can be used to con-
tain 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.
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