D8255 Programmable Peripheral Interface ver 1.00 ○ The 8-bit data port can be either input or out- OVERVIEW The D8255 is a programmable I/O device which is designed for use with all Intel and most other microprocessors. It 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 a means for transferring I/O data to or from a specified port in conjunction with strobes or „handshaking'' signals. In 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). 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 a means for communicating with a peripheral device or structure on a single 8-bit bus for both transmitting and receiving data (bidirectional bus I/O). „Handshaking'' signals are provided to maintain proper bus flow discipline in a similar manner to 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 con- trol 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 necessary to interface peripheral devices or structures. The control word register can be both written and read as shown in the address decode table in the pin descriptions. ○ Each group contains one 8-bit data port and one 4-bit control/data port. All trademarks mentioned in this document are trademarks of their respective owners. http://www.DigitalCoreDesign.com http://www.dcd.pl Copyright 1999-2007 DCD – Digital Core Design. All Rights Reserved. KEY FEATURES ● Compatible with industry standard 8255 ● 24 I/O lines individually programmed in SYMBOL 2 groups of 12: ○ Group A - Port A and upper half of Port C ○ Group B – Port B and lower half of Port C ● 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. DESIGN FEATURES datao (7:0) portai(7:0) portbi(7:0) portao (7:0) portbo (7:0) portci(7:0) portco (7:0) a(1:0) 3 major modes of operation ○ datai(7:0) we rd cs rst clk PINS DESCRIPTION PIN TYPE DESCRIPTION clk input Global clock reset input Global reset cs input Chip select rd input Processor read strobe we input Processor write strobe a[1:0] input Processor address lines portai[7:0] input Port A input portbi[7:0] input Port B input ♦ ONE GLOBAL SYSTEM CLOCK ♦ SYNCHRONOUS RESET ♦ ALL ASYNCHRONOUS INPUT SIGNALS ARE portci[7:0] input Port C input SYNCHRONIZED BEFORE INTERNAL USE datai[7:0] input Data bus (input) datao[7:0] output Data bus (output) portao[7:0] output Port A output portbo[7:0] output Port B output portco[7:0] output Port C output ♦ ALL LATCHES IMPLEMENTED IN ORIGINAL 8255 DEVICES ARE REPLACED BY EQUIVALENT FLIP-FLOP REGISTERS, WITH THE SAME FUNCTIONALITY APPLICATIONS ● Embedded microprocessor boards ● Interface to the printer ● I/O component to interface peripheral ● equipment to the microcomputer system bus BLOCK DIAGRAM Data Bus Buffer– The Data Bus Buffer is used to interface the D8255 to the system data bus. Data is transmitted or received by the buffer upon execution of input or output instructions by the CPU. Control words and status information are also transferred through the data bus buffer. Read/Write and Control Logic - The control logic block manages all of the internal and external transfers of both Data and Control or Status words. It accepts inputs from the CPU Address and Control busses and in turn, issues commands to both of the Control Groups A and B. All trademarks mentioned in this document are trademarks of their respective owners. http://www.DigitalCoreDesign.com http://www.dcd.pl Copyright 1999-2007 DCD – Digital Core Design. All Rights Reserved. Group A and Group B Controls - The functional configuration of each port is programmed by the systems software. In essence, the CPU “outputs”' a control word to the D8255. The control word contains information such as “mode”', “bit set”, “bit reset”, etc., that initializes the functional configuration of the D8255. Each of the Control blocks (Group A and Group B) accepts “commands” from the Read/Write Control Logic, receives “control words” from the internal data bus and issues the proper commands to its associated ports. Port B - One 8-bit data input/output latch/buffer. Only „pull-up'' bus hold devices are present on Port B. Port C - One 8-bit data output latch/buffer and one 8-bit data input buffer (no latch for input). This port can be divided into two 4-bit ports under the mode control. Each 4-bit port contains a 4-bit latch and it can be used for the control signal outputs and status signal inputs in conjunction with ports A and B. Only „pull-up'' bus hold devices are present on Port C. DELIVERABLES Group A - Port A and upper half of Port C Group B - Port B and lower half of Port C ♦ The control word register can be both written and read. Figure below shows the control word format for both Read and Write operations. When the control word is read, bit D7 will always be a logic “1”, as this implies control word mode information. ♦ clk rst datai datao a1 a0 rd wr cs Group A Control Data Bus Buffer & Control Logic Group B Control Group A Port A portai[7:0] Group A Port C Upper portci[7:4] Group B Port C Lower Group B Port B portao[7:0] portco[7:4] portci[3:0] portco[3:0] portbi[7:0] portbo[7:0] Source code: VHDL Source Code or/and VERILOG Source Code or/and ALTERA’s Megafunction or/and 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 ◊ Datasheet Synthesis scripts Example application Technical support ◊ IP Core implementation support ◊ 3 months maintenance ● Delivery the IP Core updates, minor and major versions changes ● Delivery the documentation updates ● Phone & email support ◊ ◊ ◊ ◊ ♦ ♦ ♦ ♦ Ports A, B, and C - The D8255 contains three 8-bit ports. All can be configured in a wide variety of functional characteristics by the system software but each has its own special features or “personality” to further enhance the power and flexibility of the D8255. Port A - One 8-bit data output latch/buffer and one 8-bit input latch buffer. Both „pull-up'' and “pulldown” bus hold devices are present on Port A. All trademarks mentioned in this document are trademarks of their respective owners. http://www.DigitalCoreDesign.com http://www.dcd.pl Copyright 1999-2007 DCD – Digital Core Design. All Rights Reserved. LICENSING CONTACTS Comprehensible and clearly defined licensing methods without royalty fees make using of IP Core easy and simply. For any modification or special request please contact to Digital Core Design or local distributors. Single Design license allows use IP Core in single FPGA bitstream and ASIC implementation. Unlimited Designs, One Year licenses allow use IP Core in unlimited number of FPGA bitstreams and ASIC implementations. In all cases number of IP Core instantiations within a design, and number of manufactured chips are unlimited. There is no time restriction except One Year license where time of use is limited to 12 months. ● Headquarters: Wroclawska 94 41-902 Bytom, POLAND [email protected] e-mail: [email protected] tel. : +48 32 282 82 66 fax : +48 32 282 74 37 Distributors: ttp://www.dcd.pl/apartn.php Please check hhttp://www.dcd.pl/apartn.php Single Design license for ○ VHDL, Verilog source code called HDL Source ○ Encrypted, or plain text EDIF called Netlist ● One Year license for ○ ● Encrypted Netlist only Unlimited Designs license for ○ HDL Source ○ Netlist ● Upgrade from ○ Single Design to Unlimited Designs ○ HDL Source to Netlist All trademarks mentioned in this document are trademarks of their respective owners. http://www.DigitalCoreDesign.com http://www.dcd.pl Copyright 1999-2007 DCD – Digital Core Design. All Rights Reserved.