DataSheet8.cn


PDF ( 数据手册 , 数据表 ) XAPP512

零件编号 XAPP512
描述 Implementing Keypad Scanners
制造商 Xilinx
LOGO Xilinx LOGO 


1 Page

No Preview Available !

XAPP512 数据手册, 描述, 功能
www.DataSheet4U.com
R
XAPP512 (v1.0) April 4, 2005
Application Note: CoolRunner-II CPLD
Implementing Keypad Scanners with
CoolRunner-II
Summary
This application note provides a functional description of Verilog source code for a keypad
scanner. The code is used to target the lowest density, 32-macrocell CoolRunnerTM-II
XC2C32A CPLD device in a CP56 package (6 mm x 6 mm). The keypad accommodated in this
design has 8 rows and 8 columns. The design can easily be scaled to target keypads with more
or less rows/columns. For instance, a keypad with 7 rows and 7 columns would allow the
design to fit in the smallest QFG32 package (5 mm x 5 mm). To obtain the Verilog source code
described in this document, see “Verilog Code,” page 4, for instructions.
Introduction
As handheld devices such as cell phones pack more and more features into them, they require
more effective ways of entering data. Most cell phones, for example, use the standard DTMF
style keypad and a multi-tap process to enter alphanumeric data; however, for larger amounts
of data multi-tapping becomes cumbersome. More and more high-end phones are therefore
employing QWERTY keypads that make entering data easier and quicker.
Going from a DTMF to a QWERTY keypad requires more I/O. For instance, a DTMF keypad
might have 4 rows and 3 columns, where a QWERTY keypad might have 8 rows and 8
columns. This can vary depending on the requirements.
Typically, a processor (or ASIC) is used to interface to the keypad’s rows and columns. The
www.DataSheet4U.comprocessor scans the rows and monitors the columns for a logic change. When a change
occurs, it indicates that one of the buttons in that column was pressed. By knowing which row
was being scanned, and which column changed state, the processor can deduce which
specific button was pushed. Additional functions such as debounce are also typically
employed. Figure 1 shows how a simple 4 x 4 keypad uses 8 GPIO of a processor.
Figure 1: Simple 4 x 4 Keypad Connected to a Processor Requiring 8 GPIO
© 2005 Xilinx, Inc. All rights reserved. XILINX, the Xilinx logo, and other designated brands included herein are trademarks of Xilinx, Inc.
All other trademarks are the property of their respective owners.
XAPP512 (v1.0) April 4, 2005
DataSheet4 U .com
www.xilinx.com
1
www.DataSheet4U.com












页数 4 页
下载[ XAPP512.PDF 数据手册 ]


分享链接

Link :

推荐数据表

零件编号描述制造商
XAPP512Implementing Keypad ScannersXilinx
Xilinx

零件编号描述制造商
STK15C88256-Kbit (32 K x 8) PowerStore nvSRAMCypress Semiconductor
Cypress Semiconductor
NJM4556DUAL HIGH CURRENT OPERATIONAL AMPLIFIERNew Japan Radio
New Japan Radio
EL1118-G5 PIN LONG CREEPAGE SOP PHOTOTRANSISTOR PHOTOCOUPLEREverlight
Everlight


DataSheet8.cn    |   2020   |  联系我们   |   搜索  |  Simemap