An improved data transfer apparatus and method is fabricated by multiplexing at least a portion of the address of the peripherals on the data bus. Data transfer is simplified by adopting identical control timing for the read and write cycles, setting up address and data information early within a cycle and synchronizing the output of such information on the output busses coupled to the peripherals. Data transfer control signals may be encoded to simplify read and write input/output and memory operations. The advantage of such improvements permits reduce component count, pin requirements and gives rise to an ability to incorporate more system functions on a single chip.
An integrated microprogrammed device for controlling information processing cycles, includes a device for generating one or more T-states in dependence on preceding T-states and on given parameters and a method for operating the device.
A microcomputer system includes a main processor, a memory and a direct memory access controller (DMA) effective to control direct data transfer between the memory and input/output devices on channels. Bus control for data transfer is switchable between the DMA and processor by a hold request/acknowledge handshaking sequence between the DMA and processor. A control line from the channels is activated by a peripheral processing device on a channel when it wishes to gain control of the busses for data transfer. Logic means coact with the handshaking sequence to determine which device gains control of the busses. This logic is responsive to the DMA address enable output (AEN), the hold acknowledge output of the main processor (HLDA) and the channel control line output (-MASTER). When all these are deactivated, control passes to the main processor, when AEN and HLDA only are activated, control passes to the DMA controller and, when all three are activated, control passes to the peripheral processing device.
A microprocessor system including a microprocessor as the central processor unit and having memory read and memory write control outputs and peripheral device read and peripheral device write control outputs. The system also includes a peripheral device and a memory connected to the microprocessor via data-, address- and control buses and provided with read and write control inputs. The system employs combinational logic circuits for controlling the interconnections of the various system devices with the microprocessor in a predetermined way.
The technique for transmitting address information between a processor and a plurality of memory subsystems in a common bus communication system. The width of the address field is greater than the number of lines on the bus. For example, addresses are three bytes wide, and the bus is one byte wide, thereby reducing the number of pins required on the processor and the subsystems. For communication between the processor and a given memory subsystem, only those bytes of a selected address which differ from the corresponding bytes of a previous address are transmitted sequentially for accessing a selected memory location.
In a microprocessor having a programmable logic array there are provided a program counter for designating an instruction data, a data bus line, a timing and control circuit for outputting an internal reset signal in response to an external reset signal, a programmable logic array that outputs a reset data signal and a reset data bus control signal by interpreting the reset signal as an instruction, and a gate circuit for sending the reset data signal to the data bus line in response to the reset data bus control signal to reset the program counter.
