INTE, elK, ElR, ETlG, ENGl, Control Signals, Int

SCHOTTKY BIPOLAR 8214

Control Signals

The 8214 also has several inputs that enable the designer to synchronize the interrupt issued to the microprocessor and to allow or disallow such an issuance. Also, signals are pro- vided that perm it simple expansion to other 8214s so that more than eight levels can be controlled.

INTE, elK

The INTE (Interrupt Enable) input allows the designer to "shutoff" the interrupt system under control of external logic or possibly under software maintenance. A "zero" on this line will not allow interrupts to be issued to the micro- computer system.

The ClK (Clock) input is actually the trigger that strobes the Interrupt Flip-Flop. It can be connected to one of the clocks of the microprocessor so that the interrupt issued meets the CPU set-up time specification. Note that due to the gating of the input to the Interrupt Flip-Flop the INT output will only be active for the time of a single clock pe- riod, so external latching may be required to hold this sig- nal.

ElR, ETlG, ENGl

These three signals allow 8214s to be cascaded so that more than eight levels of interrupt requests can be controlled.

Basically, the ENLG output of one 8214 is connected to the ETLG input of the next and so on, with the first 8214 having its ETLG input pulled "high" and assigned the high- est priority. When the ENlG output is "high" it indicates that there is no interrupt pending on that device and that interrupts can be monitored on the next lower priority 8214.

This "cascading" can be expanded almost indefinitely to accomodate even the largest of interrupt driven system arch itectu res.

AO, A1, A2

In order to identify which device has interrupted the pro- cessor so that the service routine associated with it can be addressed, a pointer or "vector" must accompany the inter- rupt issued to the microcomputer system.

The AD, A 1 and A2 outputs represent the complement of the active interrupt level (modulo 8). By using these signals to encode the special instruction, RST, the program counter of the microprocessor, can point to the location of the service routine. Note that these three outputs are gated by the ELR input and are open collector so that expansion is simplified.

INT

The INT output of the 8214 is the signal that is issued to the microprocessor to initiate the interrupt sequence. As soon a INT is active the INT DIS FF is set, inhibiting further requests from entering the Request Latch. Only the writing out of the current status information by strobing the ECS input will clear the INT DIS F F and allow requests to enter the latch.

Note that INT is also open collector so that when cascaded to other 8214s an interrupt in any of the active devices will set alllNT DIS FFs in the entire array.

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8080 specifications

The Intel 8085 and 8080 microprocessors were groundbreaking innovations in the world of computing, paving the way for future microprocessor development and personal computing.

The Intel 8080, introduced in 1974, was an 8-bit microprocessor that played a fundamental role in the early days of personal computing. With a 16-bit address bus, it had the capability to address 64 KB of memory. Running at clock speeds of 2 MHz, the 8080 was notable for its instruction set, which included 78 instructions and 246 opcodes. It supported a range of addressing modes including direct, indirect, and register addressing. The 8080 was compatible with a variety of peripherals and played a crucial role in the development of many early computers.

The microprocessor's architecture was based on a simple and efficient design, making it accessible for hobbyists and engineers alike. It included an 8-bit accumulator, which allowed for data manipulation and storage during processing. Additionally, the 8080 featured registers like the program counter and stack pointer, which facilitated program flow control and data management. Its ability to handle interrupts also made it suitable for multitasking applications.

The Intel 8085, introduced in 1976, was an enhancement of the 8080 microprocessor. It maintained a similar architecture but included several key improvements. Notably, the 8085 had a built-in clock oscillator, simplifying system design by eliminating the need for external clock circuitry. It also featured a 5-bit control signal for status line management, which allowed for more flexible interfacing with peripheral devices. The 8085 was capable of running at speeds of up to 3 MHz and had an extended instruction set with 74 instructions.

One of the standout features of the 8085 was its support for 5 extra instructions for stack manipulation and I/O operations, which optimized the programming process. Additionally, it supported serial communication, making it suitable for interfacing with external devices. Its 16-bit address bus retained the 64 KB memory addressing capability of its predecessor.

Both the 8080 and 8085 microprocessors laid the groundwork for more advanced microprocessors in the years that followed. They demonstrated the potential of integrated circuits in computing and influenced the design and architecture of subsequent Intel microprocessors. Their legacy endures in the way they revolutionized computing, making technology accessible to a broader audience, and their influence is still felt in the design and architecture of modern microprocessors today.

Intel 8080 manual INTE, elK, ElR, ETlG, ENGl, Control Signals, AO, A1, A2, Int

Models: 8080