Abstract: A dual-port memory which features a pipelined serial port is disclosed. The serial side of the dual-port memory contains a ripple counter which is broken between predetermined stages. The contents of the stages above the break are decoded to select a group of bits of the serial register for output, and the contents latched in a latch. In serial output, the contents of the stages below the break are decoded, so that responsive to the stages below the break reaching a certain value, the stages above the break are incremented and the incremented value decoded. Pass transistors between the register and the latch are turned off during such time as the incremented value is being decoded, so that the new value will not disturb the output. The latched output is selectively presented by a multiplexer which selects the latch bits responsive to the value of the stages below the break. Upon the value of the stages reaching its minimum value (i.e.

Abstract: A dual-port memory which features a pipelined serial port is disclosed. The serial side of the dual-port memory contains a ripple counter which is broken between predetermined stages. The contents of the stages above the break are decoded to select a group of bits of the serial register for output, and the contents latched in a latch. In serial output, the contents of the stages below the break are decoded, so that responsive to the stages below the break reaching a certain value, the stages above the break are incremented and the incremented value decoded. Pass transistors between the register and the latch are turned off during such time as the incremented value is being decoded, so that the new value will not disturb the output. The latched output is selectively presented by a multiplexer which selects the latch bits responsive to the value of the stages below the break. Upon the value of the stages reaching its minimum value (i.e.

Abstract: A dual-port random access memory with multiple random inputs is disclosed which has a write mask register. The write mask allows a random write operation to occur on a subset of the random inputs, with the selected memory cells remaining undisturbed by the write operation. The write mask register provides for storage of the write mask information for a plurality of cycles, including intervening cycles which are unmasked writes. The write mask register may be loaded in two separate modes, either early in a cycle in conjunction with the row address strobe signal, or later in the cycle in conjunction with the write enable signal.

Abstract: A dual-port memory having a special operating mode (i.e., a block write mode) by which a plurality of memory cells may be written with the same data in a single write cycle is disclosed. The special mode is enabled by a special function pin in conjunction with the write enable and transfer enable function pins, each of which have their logic state latched in during the row address strobe signal. The column decoder in this device is in two stages, where the first stage selects a group of columns based upon the most significant column address bits. The second stage selects a single column based upon the least significant column address bits. In the block write mode, the result of the second column address decoder stage is ignored, and another set of signals select one, more than one, or all of the columns in the group for connection to the input/output circuitry, so that the same data is written to a plurality of memory locations within a certain column address proximity.

Abstract: A semiconductor memory is comprised of four arrays (10), (12), (14) and (16) that have the memory elements therein arranged in accordance with pixel positions on a display. The memory arrays have associated shift registers (34), (36), (38) and (40) which have data loaded in parallel and output in a serial format to the display. Each of the shift registers can be connected in a circulating fashion or a shift register of adjacent arrays can be cascaded. Switches (56), (58), (60) and (62) are provided for configuring the shift registers for either circulation or cascading of data. In the circulating mode, the input and output of the shift registers is multiplexed on one pin whereas in the cascaded configuration, one array receives a dedicated serial input and the other array in the cascaded pair outputs the serial output on a dedicated pin.

Abstract: In a video-type computer system and the like, an improved memory circuit is provided for adapting the system to CRT screens having different resolutions. The memory circuit includes a bit-mapped RAM unit or chip having sufficient cells to accommodate any CRT screen sought to be used, and also a shift register having taps at a plurality of different locations corresponding to different columns of cells in the RAM unit. When the RAM unit is in serial mode, column address to the RAM unit is also used to instruct and actuate a suitable decoder circuit to select the tap appropriate to unload the portion of the shift register containing only the data bits of interest.

Abstract: In a video computer system and the like having a bit-mapped RAM component including a shift register, an improved method is provided for rapidly clearing the RAM in order to prepare the system to receive new input data. More particularly, a preselected number of predetermined data bits corresponding to the number of columns in the RAM is serially shifted into the register. Thereafter, the contents of the shift register are progressively shifted into each of the rows in the RAM until all rows are filled.

Abstract: In video computer system having a dual-port bit-mapped RAM unit incorporating a shift register, provision is made for coupling data between column lines and the shift register, and for simultaneously preventing any column line from being coupled with the random data output terminal of the RAM unit. Accordingly, this prevents two or more different data bits from appearing simultaneously from the RAM unit and causing confusion as to which is the valid signal and which is a spurious signal.

Abstract: A semiconductor memory is comprised of four arrays (10), (12), (14) and (16) that have the memory elements therein arranged in accordance with pixel positions on a display. The memory arrays have associated shift registers (34), (36), (38) and (40) which have data loaded in parallel and output in a serial format to the display. Each of the shift registers can be connected in a circulating fashion or a shift register of adjacent arrays can be cascaded. Switches (56), (58), (60) and (62) are provided for configuring the shift registers for either circulation or cascading of data. In the circulating mode, the input and output of the shift registers is multiplexed on one pin whereas in the cascaded configuration, one array receives a dedicated serial input and the other array in the cascaded pair outputs the serial output on a dedicated pin.

Abstract: A semiconductor memory comprises four arrays (10), (12), (14) and (16) disposed on a single semiconductor chip. Each of the arrays has a serial shift register (86) associated therewith. Data is transferred from the bit lines of the associated array through a transfer gate (90) for storage in the shift register (86). A tap latch (88) is provided on the output of each of the shift bits in the shift register (86) for determining the output therefrom. The tap latch (88) stores a tap decode signal which is decoded from a tap address by the column decoder (30). The column decoder (30) also decodes the column address in the random mode. The tap decode signal selects any of the shift bits in the shift register (86).

Abstract: A video memory controller controls a DRAM (dynamic random access memory) used as a video memory and as a system memory. The video memory and the video memory controller are normally a part of a video system which includes a data processor, the video memory, the video memory controller, a CRT controller and a CRT display device. The video memory controller includes a row address latch for storing a row address from the data processor, a column address latch for storing a column address from the data processor, a refresh address register for storing a memory refresh address and a display update generator for sequentially generating the addresses necessary for update of the CRT display. A multiplexer couples the proper address to the video memory under control of a memory cycle generator which generates the timing of the memory refresh and display update. An arbiter device enables only one of the possible memory cycles at a time.

Abstract: A semiconductor memory circuit includes memory arrays (10), (12), (14) and (16). Each of the memory arrays has associated therewith shift registers (34), (36), (38) and (40). Transfer gates (54) are disposed between the memory arrays and the associated shift registers. A control circuit (69) is provided for receiving an external transfer signal and transferring the data between the arrays and the associated shift registers. The shift registers are clocked in response to receiving an external shift clock signal to serially output data therefrom. A delay circuit (292) is provided for delaying shifting of data for a predetermined duration to ensure that a complete transfer of data has been effected. Transfer of data is inhibited until the occurrence of the XBOOT signal by circuit (296) to provide for early occurrence of the transfer signal. Data access is maintained by a delay circuit (330) to accommodate late occurrence of the transfer signal by delaying the internal row address strobe.

Abstract: In a computer system, an improved memory circuit is provided for accomodating video display circuits with CRT screens having different resolutions. The memory circuit includes a bit-mapped RAM unit or chip having sufficient cells to accomodate any CRT screen intended to be used, and it further includes a serial shift register having a plurality of taps at locations corresponding to different preselected columns of cells in the chip. In the system, provision is included for selecting taps to unload only the portion of the shift register containing the bits of interest, whereby unused portions of the chip may be effectively excluded and the time for transferring data of interest to the CRT screen is reduced.

Abstract: A circuit for inhibiting data transfer to addressed memory locations in a plurality of arrays on a semiconductor chip includes an arbitration circuit (68) that distinguishes between separate inhibit signal inputs on dedicated CAS terminals and multiplexed inhibit signals on the input of an I/O buffer (66). The arbitration circuit (68) controls the enable circuits (64) for transferring data from the I/O buffer (66) to memory arrays (10), (12), (14) and (16). Separate inhibit signals allow multiple arrays to share common row and column decoders and maintain separate read/write capability.