DS12887A Datasheet, PDF (4/19 Pages) Maxim Integrated Products – Real-Time Clock

DS5000(T)
PIN NUMBER
32–39
40
DESCRIPTION
P0.7–P0.0. General purpose I/O Port 0. This port is open–drain and can not drive a
logic 1. 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.
V_CC – +5 volts.
INSTRUCTION SET
The DS5000(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 DS5000(T), including cross–as-
semblers, high–level language compilers, and debug-
ging tools.
A complete description for the DS5000(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 DS5000(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 64K bytes of program
memory and 64K bytes of data memory can be ac-
cessed by the DS5000(T) CPU. The 8K or 32K byte
RAM area inside of the DS5000(T) can be used to con-
tain both program and data memory.
The Real time Clock (RTC) in the DS5000T 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.
If the ECE2 bit is set on a DS5000 without a timekeeper,
the MOVXs will simply go to a nonexistent memory.
Software execution would not be affected otherwise.
021998 4/19