Book contents
- Frontmatter
- Contents
- 1 Introduction
- 2 Instrumentation structures and using the IBM-PC
- 3 Thermistor experiments
- 4 Timing
- 5 Thermal diffusion
- 6 IBM-PC architecture and assembly language programming
- 7 Viscosity measurement
- 8 Interrupts
- 9 Other topics
- Appendix A Laboratory materials and sources
- Appendix B Graphing programs and disk configuration
- Appendix C IBM-PC memory map
- Appendix D Connections and logic of the ADC
- Appendix E 8255 Programmable Peripheral Interface data sheets
- Appendix F Solution for heat flow in one dimension
- Appendix G Finite impulse heat flow in a rod
- Appendix H 8088 Microprocessor data sheets
- Appendix I 8253 Programmable interval timer data sheets
- Appendix J 8250/8251 Programmable Communication Interface
- Appendix K Bibliography and sources
- Index
Appendix J - 8250/8251 Programmable Communication Interface
Published online by Cambridge University Press: 03 February 2010
- Frontmatter
- Contents
- 1 Introduction
- 2 Instrumentation structures and using the IBM-PC
- 3 Thermistor experiments
- 4 Timing
- 5 Thermal diffusion
- 6 IBM-PC architecture and assembly language programming
- 7 Viscosity measurement
- 8 Interrupts
- 9 Other topics
- Appendix A Laboratory materials and sources
- Appendix B Graphing programs and disk configuration
- Appendix C IBM-PC memory map
- Appendix D Connections and logic of the ADC
- Appendix E 8255 Programmable Peripheral Interface data sheets
- Appendix F Solution for heat flow in one dimension
- Appendix G Finite impulse heat flow in a rod
- Appendix H 8088 Microprocessor data sheets
- Appendix I 8253 Programmable interval timer data sheets
- Appendix J 8250/8251 Programmable Communication Interface
- Appendix K Bibliography and sources
- Index
Summary
This device is commonly called a UART (Universal Asynchronous Receiver/Transmitter). There is one for each COM port of the computer. They allow communication between computers directly or via telephone modems.
Asynchronous Communications Adapter
The Asynchronous Communications Adapter is a 4“H × 5”W card that plugs into a System Expansion Slot. All system control signals and voltage requirements are provided through a 2 × 31 position card edge tab. A jumper module is provided to select either RS-232-C or current loop operation.
The adapter is fully programmable and supports asynchronous communications only. It will add and remove start bits, stop bits, and parity bits. A programmable baud rate generator allows operation from 50 baud to 9600 baud. Five, six, seven or eight bit characters with 1, 1–1/2, or 2 stop bits are supported. A fully prioritized interrupt system controls transmit, receive, error, line status and data set interrupts. Diagnostic capabilities provide loopback functions of transmit/receive and input/output signals.
Figure (22) is a block diagram of the Asynchronous Communications Adapter.
The heart of the adapter is a INS8250 LSI chip or functional equivalent. The following is a summary of the 8250's key features:
Adds or Delete Standard Asynchronous Communication Bits (Start, Stop, and Parity) to or from Serial Data Stream.
Full Double Buffering Eliminates Need for Precise Synchronization.
Independently Controlled Transmit, Receive, Line Status, and Data Set Interrupts.
Programmable Baud Rate Generator Allows Division of Any Input Clock by 1 to (216–1) and Generates the Internal 16× Clock.
Independent Receiver Clock Input.
- Type
- Chapter
- Information
- IBM-PC in the Laboratory , pp. 216 - 239Publisher: Cambridge University PressPrint publication year: 1990