The D8255 is a programmable I/O device, designed to be used with all Intel CPUs. What's significant, it also supports most other microprocessors. Our onnovative IP core provides 24 I/O pins, which may be individually programmed in 2 groups of 12 and used in 3 major modes of operation:
* Mode 0 - Basic Input/Output. This functional configuration provides simple input and output operations for each of the three ports. No ?handshaking'' is required, data is simply written to or read from a specified port. Mode 0 Basic Functional Definitions:
- Two 8-bit ports and two 4-bit ports
- Any port can be input or output
- 16 different Input/Output configurations are possible in this Mode.
* MODE 1 - Strobed Input/Output. This functional configuration provides means for transferring I/O data to or from a specified port in conjunction with strobes or ?handshaking'' signals. In the mode 1, Port A and Port B use the lines on Port C, to generate or accept these ?handshaking'' signals. Mode 1 Basic functional Definitions:
- Two Groups (Group A and Group B).
- Each group contains one 8-bit data port and one 4-bit control/data port.
- The 8-bit data port can be either input or out-put Both inputs and outputs are latched.
- The 4-bit port is used for control and status of the 8-bit data port.
* MODE 2 - Strobed Bidirectional Bus I/O. This functional configuration provides means for communicating with a peripheral device or structure on a single 8-bit bus, both for transmitting and receiving data (bidirectional bus I/O). ?Handshaking'' signals are provided to maintain proper bus flow discipline in a similar manner to the MODE 1. Interrupt generation and enable/disable functions are also available. MODE 2 Basic Functional Definitions:
- Used in Group A only.
- One 8-bit, bi-directional bus port (Port A) and a 5-bit control port (Port C).
- The 5-bit control port (Port C) is used for control and status for the 8-bit, bi-directional bus port (Port A).
The functional configuration of the D8255 is programmed by the system software, so that normally no external logic is needed to interface peripheral devices or structures. The control word register can be both written and read, as it has been shown in the address decode table (please, see the pin descriptions).
- Compatible with industry standard 8255
- 24 I/O lines individually programmed in 2 groups of 12:
- Group A - Port A and upper half of Port C
- Group B - Port B and lower half of Port C
- 3 major modes of operation
- Mode 0 - Basic input/output
- Mode 1 - Strobed Input/output
- Mode 2 - Bi-directional Bus
- Control Word Read-Back Capability
- Direct Bit Set/Reset Capability
- Interrupt control functions
- No internal three states busses
- Fully synthesizable, technology independent source code.
- Getting a silicon proven and technologically independent IP (VHDL and Verilog)
- Rapid prototyping and time-to-market reduction
- Design risk elimination
- Development costs reduction
- Full customization
- Wide range of peripherals
- Global sales network
- Professional service
- Fast responsive support
- Source code:
- VHDL Source Code or/and
- VERILOG Source Code or/and
- Encrypted, or plain text EDIF netlist
- VHDL & VERILOG test bench environment
- Active-HDL automatic simulation macros
- ModelSim automatic simulation macros
- Tests with reference responses
- Technical documentation
- Installation notes
- HDL core specification
- Synthesis scripts
- Example application
- Technical support
- Embedded microprocessor boards
- Interface to the printer
- I/O component to interface peripheral
- Equipment to the microcomputer system bus