Motorola Corporation

Gregory A Racino

James Robert Feddeler

James S Thomas

Vincent B Deems

Laura M Dobbs

Jeffrey R Jorvig

Kenneth Obuszewski

Robert W Sparks

Donald G Weiss

Brian R Gardner

Victor E Shiff

An integrated circuit (20) includes an ESD protection circuit (50) to protect it from excessive electrostatic discharge voltages. The ESD protection circuit (50) includes a diode (51) in series with a silicon controlled rectifier (SCR) (60) connected between an input signal line (42) and a power supply voltage terminal. Unlike conventional protection circuits, the ESD protection circuit (50) allows the voltage on the input signal line (42) to extend well beyond positive and negative power supply potentials, and only becomes conductive to discharge voltages which are outside of this extended range.

Integrated circuit with electrostatic discharge (ESD) protection and ESD

A pseudo-static mask option register (50) combines features of both a continuous refresh design and a static latched mask option register design. Pseudo-static mask option register (50) removes a mask option function from a main user memory (48) such that the functionality of the mask option register (50) is not limited by a plurality of electrical characteristics of the main use memory (48). When using the pseudo-static mask option register (50), a memory state of each memory bit (64, 66, 68) is read at any time. Additionally, a portion of the memory bits (64, 66, 68) is periodically refreshed such that pseudo-static mask option register (50) maintains an integrity of a value stored therein while minimizing power consumption. Pseudo-static mask option register (50) also has a non-volatile output state to allow emulation of mask options which are vulnerable to electrical disturbances.

Pseudo static mask option register and method therefor

A method and apparatus for preventing a data processing system (10) from entering a non-recoverable state. In one form, the present invention uses a pin (40) to indicate whether or not the execution of a non-recoverable instruction is legal. If the pin indicates that the execution of the instruction is legal, then the instruction is executed and the data processing system (10) is placed into a state that requires an external stimulus in order to recover. If the pin indicates that the execution of the instruction is illegal, then the instruction is not permitted to place the data processing system (10) into a state that requires an external stimulus in order to recover. Instead, an internal recovery mechanism is provided which returns the data processing system (10) to normal processing.

Method and apparatus for preventing a data processing system from

A nonvolatile memory (28) in a data processor (10) is capable of being progressively programmed and/or accessed in a user determined number of sections. A user can program and/or access what appears to the user to be reprogrammable nonvolatile memory (28) at a same address when in actuality the user is programming and accessing sequential sections of nonvolatile memory (28). Nonvolatile information stored in nonvolatile control bits (20) is used to control which section of the nonvolatile memory is connected to a communication bus and is thus accessible to the user. When the user desires to write and/or access a new section of nonvolatile memory (28), either the user directly asserts one of the nonvolatile control bits (20) using software, or the nonvolatile control (24) asserts one of the nonvolatile control bits (20) using hardware.

Technique to support progressively programmable nonvolatile memory

A method and apparatus for performing power on reset initialization in a data processing system (40). In one form, the present invention uses a circuit (71) to ensure that a node (65) always power up to the correct logic level. This node (65) can then be used to initialize a latch (83) so that the latch (83) always drives a predetermined logic level at its data output when the latch (83) powers up. The data output of latch (83) is a Power On Reset signal which is asserted during power on reset initialization and which is negated when power on reset initialization is completed.

Method and apparatus for performing power on reset initialization in a

A microcontroller is provided having an on-chip electrically erasable programmable read-only-memory (EEPROM), which is user programmable via a programming register. The microcontroller includes a low voltage program inhibit (LVPI) circuit which is combined with the existing EEPROM design. By integrating the LVPI circuit into the EEPROM, the EEPROM may be protected without disabling the entire data processing system. If the supply voltage (V.sub.DD) falls below a predetermined voltage level, the LVPI circuit inhibits the use of the EEPROM programming register, thereby preventing the CPU from programming or erasing the EEPROM. A comparator in the LVPI circuit compares a precision reference voltage to a voltage divided off of the power supply (V.sub.DD), and provides a output signal to the EEPROM programming register. During normal operation, the comparator output signal is a logic low, which enables the user to program or erase the EEPROM, via the programming register. When the supply voltage is below the predetermined safe level, the comparator output signal is a logic high signal, which sets a control bit in the programming register. When set, the control bit clears the remaining bits in the programming register, thereby disabling a charge pump, and preventing any further EEPROM programming.

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Austin, TX, United States of America

Gregory A Racino