An information transferring apparatus disposed between first and second information processing units comprises a first-in first-out stack, a first information line for transferring information from the first information processing unit to the first-in first-out stack, a second information line for transferring information from the first-in first-out stack to the second information processing unit, a third information line for transferring information from the second information processing unit to the first-in first-out stack, a fourth information line for transferring information from the first-in first-out stack to the first information processing unit, switching circuits for selectively deactivating the first to fourth information lines, and a command register for applying first and second control signals to the switching circuits, wherein the switching circuits operate responsive to the first control signal from the command register to deactivate the third and fourth information lines while holding active the first and second information lines, and operate responsive to the second control signal from the command register to deactivate the first and second information lines while holding active the third and fourth information lines. The command register may be replaced and its functions performed by either manual control or an external circuit.
Apparatus for producing a circular-queue structure which permits interfacing between a high speed mini-computer and a relatively slow speed microprocessor via a common memory and with multi-device, asynchronous handling capability. The structure also permits commands and data to be chained in the same queue. The apparatus permits multiple devices to be handled simultaneously. By monitoring the memory address which is being accessed by the minicomputer, the information retrieved from the memory by the microprocessor is selectively validated or invalidated.
A personal computer attachment is provided for a display station of the type that communicates with a host computer (48). The display station has a display unit (10) and a keyboard (12) to which a personal computer system unit (14) is attached. The personal computer system unit typically supports floppy diskette drives (16) and a printer (18). The display unit includes a CRT (38), a regeneration buffer (42), a keyboard adapter (46) and a feature bus (44). The personal computer system unit includes a system bus, a microprocessor, memory, a keyboard adapter and I/O interface connected to the system bus. A display adapter (26 or 28) is connected to the I/O interface. An analog input switch (52) is disposed between the buffer (42) and the analog circuits driving the CRT (38). This switch has a second input from the display adapter (26 or 28) and is controlled from inputs from the keyboard (12) to selectively supply image data from the buffer (42 ) or the display adapter (26 or 28). An attachment adapter (36) mates with the I/O interface of the personal computer system unit. The adapter (36) includes an input/output interface (54), a switch control (56), a two-way keyboard adapter (58) and a feature bus adapter (60). The keyboard (12) is connected to the two-way keyboard adapter (58). Each of the switch control (56), the two-way keyboard adapter (58) and the feature bus adapter (60) communicate with the system bus of the personal computer system unit via the input/output interface. The switch control (56) is also connected to the control input of the analog input switch (52). The two-way keyboard adapter (58) is also connected to the keyboard adapter in the display station and the keyboard adapter in the personal computer system unit. The feature bus adapter (60) is also connected to the feature bus (44) of the display station. This arrangement allows keystroke signals from the keyboard (12) to be transmitted by the two-way keyboard adapter (58) via the input/output interface (54) and system bus to the memory in the personal computer system unit for interpretation by the microprocessor and then retransmitted back to the two-way keyboard adapter and then to a designated one of the keyboard adapters in either the display station or the personal computer system unit. The switch control is responsive to a unique keystroke signal to control the analog input switch (52). In this way, the operator can control the mode of operation between either a host mode or a personal computer mode. Further, data transfer can be made between the host computer and the personal computer.
The present invention provides for at least two levels of buffering in compensating for the delays from and out of the Unix workstation, thus achieving the required timebase correction. At the first level of buffering there is an eight Megabyte memory coupled to the VME bus of the Unix workstation over a disc simulator processor, which is sufficient to store about 45 seconds of audio data. The secondary level of data buffering is provided by an interface board which further buffers an additional 1.5 milliseconds between the first level of buffering and the second level of buffering. The outbound interface of the present invention comprises three separate registers to process the compact disc data when they are retrieved from the digital computer. Each of the registers comprises a plurality of FIFO registers. The first register receives outbound audio samples. The second register receives Q subcode data. The third register receives optionally QRSTUVW or RSTUVW subcode data. Instead of burdening the Unix software with the task of interleaving the subcodes, the present invention manages and manipulates the subcodes with the hardware of the interface. An inbound interface similar to that of the outbound interface is also provided for receiving and storing compact disc data. Thus, the present invention can store and replay compact disc data simultaneously.
