DS2252T Datasheet, PDF (5/15 Pages) Dallas Semiconductor – Secure Microcontroller Module

PIN
22
35, 37
39
2
24
20
DS2252T
DESCRIPTION
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.
V_CC - +5V.
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 microcontroller will enter
Bootstrap loading on power up. This signal is pulled up internally.
SDI – Self-Destruct Input. A logic 1 applied to this input causes a hardware unlock. This
involves the destruction of Encryption Keys, Vector RAM, and the momentary removal of
power from V_CCO. This pin should be grounded if not used.
INSTRUCTION SET
The DS2252T executes an instruction set that is object code-compatible with the industry standard 8051
microcontroller. As a result, software development packages such as assemblers and compilers that have
been written for the 8051 are compatible with the DS2252T. A complete description of the instruction set
and operation are provided in the User’s Guide section of the Secure Microcontroller Data Book.
MEMORY ORGANIZATION
Figure 2 illustrates the memory map accessed by the DS2252T. The entire 64k of program and 64k of
data are available to the Byte-wide bus. This preserves the I/O ports for application use. An alternate
configuration allows dynamic Partitioning of a 64k space as shown in Figure 3. Any data area not mapped
into the NV RAM is reached via the Expanded bus on Ports 0 and 2. Off-board program memory is not
available for security reasons. Selecting PES=1 provides access to the Real Time Clock as shown in
Figure 4. These selections are made using Special Function Registers. The memory map and its controls
are covered in detail in the User’s Guide section of the Secure Microcontroller Data Book.
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