One intermediate shale used for parallel interfacing is the Programmable Peripheral Interface (PPI) 8255. This flake is manufactured by Intel Corporation and packaged in the form of a 40 pin dual in line package and designed for a variety of interface functions in the microprocessor. PPI 8255 has 24 I / O pins which are divided into three 8-bit ports. These ports are port A (PA0-PA7), port B (PB0-PB7) and port C (PC0-PC7). As a path for transferring data to and from PPI 8255 an 8 bit data bus channel (D0-D7) is provided. The data bus from this PPI can be connected directly to the data bus from a microcomputer.
The IN91531N provides a 4-bit data input and a handshaking signal to serve as microcomputer interfaces. Under microcomputer control the IN91531N generates both a DTMF signal and a pulse output for telephone dialing. All necessary dual -tone frequencies and dial pulse outputs are derived from the widely used TV crystal standard, providing high accuracy and stability. The required sinusoidal waveform for individual tones is digitally synthesized on the chip, resulting in a waveform with very low total harmonic distortion.
1. TTL compatible inputs and outputs 2. Uses TV crystal standard (3.58 MHz) to derive all frequencies, providing high accuracy and stability 3. Operating voltage: 2.5 to 5.5 Volts 4. Selectable M/B ratio 5. 10 PPS dial rate 6. High group tone pre-emphasis : 2 dB 7. Low total harmonic distortion in DTMF signaling
Other data sheets within the file : 91531, IL91531N