Abstract: A processor fabricated in a semiconductor chip has on-chip program memory and access to off-chip program memory. Switching between the on-chip memory and the off-chip memory is effected in the course of program execution, without using a pin-out of the device package in which the processor is housed or encapsulated, by writing a system configuration bit stored in a memory location shared by the on-chip and off-chip memories to a "1" or a "0" according to whether the program instruction is to be executed from the on-chip memory or the off-chip memory.

Abstract: The RAM includes sub-arrays having odd and even memory locations, respectively. A data move instruction results in externally generated row and column address signals which are decoded to cause a first memory location, in one of the sub-arrays, to be selected and data to be read. The next memory location in sequence, in the other of the sub-arrays, is then selected, without necessity for an additional set of row address signals, for writing of the read information. The row decoder includes row indexing circuitry actuatable upon receipt of a shift signal signifying that the first memory location is in the last column of a given row. When the shift signal is received, the write location is automatically selected to be in the succeeding row.

Abstract: A semiconductor integrated circuit device has an on-chip processor and at least one on-chip digital register for storing plural bits therein. The bit contents of the register are written, selectively transformed, and read out of the register during processing of data by the processor and related circuitry. Peripheral instructions such as those from an interrupt source may contend with instructions from the processor for setting and clearing one or more bits in the register. To permit setting and clearing a unique bit in the register without affecting other bits in the register or the capability of the contending source to perform its instructions on one or more of these other bits, three separate addresses are provided for bit set, bit clear, and direct write of the register.

Abstract: The processor executes programs from an internal EEPROM or from an external source. The EEPROM can be read either by a special operating (test) mode of the processor or by an instruction executing under normal operating mode from the EEPROM or from an external source. Similarly, the EEPROM can be programmed (written) either by a special operating mode or by under a normal operating mode instruction. The read and write circuits for the EEPROM are controlled to provide two levels of security against piracy of programmed information. In the first level, access is prevented for the read and write test modes and also for the read and write normal operating instructions if the instructions originate from an external source. In the second level, program execution from external source is also disabled.