Abstract: A main memory system includes encoder and decoder circuits. The encoder circuits are connected to receive data bits and parity bits and from them generate check code bits which are stored with the data bits during a write cycle of operation. The decoder circuits are connected to receive data and check bits read out from memory during a read cycle of operation. The decoder circuits include a plurality of decoder circuits and error locator circuits. Circuits via exclusive OR circuits generate a number of syndrome bit signals. These signals are divided into first and second groups. The first group is coded to specify which one of a number of decoder circuits comprising the error locator circuits is to be enabled in the case of an error condition. The second group of signals is coded to designate the particular data bit to be corrected by the decoder circuits.

Abstract: Apparatus and method are included in the main memory of the data processing system which receives data from a plurality of input/output devices connected to a common bus. During a write cycle of operation, a device applies a plurality of data byte signals together with associated parity bits for writing into an addressed storage location of memory. Error detection and correction encoder circuits are connected to receive the data bits and parity bits and from them generate check code bits which are coded to signal selectively the presence of an uncorrectable error condition in accordance with the parity bits from a given source.

Abstract: Apparatus and a method for generating timing signals to be utilized in latched type memories only when the address signals are valid. A CAS signal is generated in response to an RAS signal via a device which tracks the worst case delay of memory address signals and does not permit the application of the CAS signal to memory until the worst case delay of the memory address signals has been accounted for.A memory array is comprised of any combination of latched or non-latched tri-state memories. The latched memories are coupled to a data bus utilizing conventional TTL circuits in combination with a power driver to simulate conventional tri-state buffer circuits. When the power driver/drivers remove(s) power from TTL circuits, the tri-state characteristics are simulated; whereas when the power driver applies power to the TTL circuits, they operate in their normal mode and present a normal impedance between the data bus and data-out lines of the memory array.

Abstract: Apparatus and a method for coupling and uncoupling data-read lines of a memory array to a data bus. The data read-out lines of a memory array which is comprised of any combination of latched or non-latched tri-state memories are coupled to the data bus utilizing a conventional TTL circuit in combination with a power driver to simulate a tri-state buffer circuit. When the power driver removes power from the TTL circuit, a tri-state circuit is simulated; whereas when the power driver applies power to the TTL circuit, it operates in its normal mode and a normal impedance is presented between the data bus and the data-out lines of the memory array.