Future Technology Devices International Ltd. 2006 AN232B-05 Confi

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Future Technology Devices International Ltd. 2006 AN232B-05 Confi

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AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates
Table Contents
Part Setting Baud Rates FT232R, FT2232C FT232BM Devices
Introduction Setting Baud Rate Baud Rate Calculation
Part Aliasing Baud Rates
Aliasing Aliasing Using Original Sub-Integer Divisors Aliasing Using Additional FT232BM Sub-Integer Divisors
Part Revision History, Disclaimer, Contact Information
Document Revision History Disclaimer Contact Information
Index
Future Technology Devices International Ltd. 2006
Setting Baud Rates FT232R, FT2232C FT232BM Devices
Setting Baud Rates FT232R, FT2232C FT232BM Devices
Introduction
most basic operations with FT232R, FT2232C (UART mode) FT232BM devices setting Baud rate. This application note describes various ways that this done. also describes non-standard baud rates with FTDI's USB-Serial devices, including technique called 'aliasing' where Baud rate substituted driver place another baud rate. second generation FT232BM UART added additional granularity divisor used generate device Baud rate. This allows much larger number baud rates used with FT232BM when compared predecessor, FT8U232AM.
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates
Setting Baud Rate
When using FTDI Virtual Port (VCP) drivers, Baud rate Device Manager from application. When Baud rate from application program done exactly same with standard Windows Port simply passing required Baud rate port using Windows VCOMM calls Port library. Both standard nonstandard baud rates this manner. When using FTDI's D2XX direct driver function FT_SetBaudRate used both standard non-standard baud rates. non-standard Baud rate required formulae this application note used determine possible. required non-standard Baud rate possible simply pass driver normal required divisor will calculated driver. D2XX there longer need function FT_SetDivisor, been left backward compatibility.
Future Technology Devices International Ltd. 2006
Setting Baud Rates FT232R, FT2232C FT232BM Devices
Baud Rate Calculation
Baud rate FT232R, FT2232C (UART mode) FT232BM generated using chips internal 48MHz clock. This input Baud rate generator circuitry where then divided into prescaler 3MHz reference clock. This 3MHz reference clock then divided down provide required Baud rate device's chip UART. value Baud rate divisor integer plus sub-integer prescaler. original FT8U232AM only allowed subinteger prescalers 0.125, 0.25 0.5. FT232R, FT2232C (UART mode) FT232BM support further additional sub-integer prescalers 0.375, 0.625, 0.75, 0.875. Thus, allowed values Baud rate divisor are: Divisor 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875; where integer between 16384 (214). Note: Divisor Divisor special cases. divisor will give MBaud, divisor will give MBaud. Sub-integer divisors between allowed. Therefore value divisor needed given Baud rate found dividing 3000000 required Baud rate. exact Baud rate achievable however long actual Baud rate used within +/-3% required Baud rate then link should function without errors. When Baud rate passed driver where exact divisor required achievable closest possible Baud rate divisor will used long that divisor gives Baud rate which within Baud rate originally set. example: non-standard Baud rate 490000 Baud required. Required divisor 3000000 490000 6.122 closest achievable divisor 6.125, which gives baud rate 489795.9, which well within allowed margin error. Therefore 490000 passed driver device will communicate without errors.
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates
Aliasing Baud Rates
Aliasing
file FTDIPORT.INF contains entries that used divisors standard Baud rates. changing these possible alias standard Baud rates with non-standard values instance replacing 115kBaud with 512kBaud. Users would then FT232R, FT2232C (UART mode) FT232BM operate 512kBaud selecting 115kBaud appropriate serial port.
Future Technology Devices International Ltd. 2006
Aliasing Baud Rates
Aliasing Using Original Sub-Integer Divisors
There sections file FTDIPORT.INF which changed Windows Windows Millennium Edition other Windows 2000 entry Windows shown below with relevant fields highlighted bold. Note entry Windows 98/ME very similar changed following same steps. found under header FtdiPort232.HW.AddReg. [FtdiPort232.NT.HW.AddReg] D,00,06,40,03,80,00,00,d0,80 Each field consists pair bytes, ordered follows: Byte0,Byte1. Bits through denote integer divisor while bits denote sub-integer divisor, follows 15,14 sub-integer divisor 15,14 sub-integer divisor 15,14 sub-integer divisor 0.25 15,14 sub-integer divisor 0.125 divisor extracted each entry simple steps, shown here entry 9c,80 Step re-order bytes: 9c,80 809c Step extract sub-integer divisor; sub-integer 0.25 Step extract integer divisor: 13:0 009c Step combine integer sub-integer divisors: 156.25 Step divide 3000000 divisor=> 3000000/156.25 19,200 baud following lists standard values their respective baud rates. 10,27 divisor 10000, rate 88,13 divisor 5000, rate C4,09 divisor 2500, rate 1200 E2,04 divisor 1250, rate 2,400 71,02 divisor 625, rate 4,800 38,41 divisor 312.5, rate 9,600 9C,80 divisor 156, rate 19,230 4E,C0 divisor rate 38,461 34,00 divisor rate 57,692 1A,00 divisor rate 115,384 0D,00 divisor rate 230,769 06,40 divisor 6.5, rate 461,538 03,80 divisor 3.25, rate 923,076 00,00 RESERVED D0,80 divisor 208.25, rate 14406 alias baud rate 920k baud standard baud menu option under windows: change 34,00 entry 03,80 (simple both values available from previous list) alias rate 197k baud standard 4,800 baud menu option under windows find best divisor, check that sufficiently accurate then modify appropriate file entry.
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates 3,000,000/197,000 15.228. best divisor 15.25. 3,000,000/15.25 196,721. 196,721/197,000 99.8%. This well within required tolerance. 15:14 sub-integer divisor 0.25, lower bits replace 71,02 entry with 0F,80. Incorporating these changes FTDIPORT.INF entry becomes [FtdiPort232.NT.HW.AddReg] D,00,06,40,03,80,00,00,00,00 This Windows 2000 changes should repeated Windows 98/ME entry also.
Future Technology Devices International Ltd. 2006
Aliasing Baud Rates
Aliasing Using Additional FT232BM Sub-Integer Divisors
standard FTDIPORT.INF ConfigData Baud rate table only supports original FT8U232AM sub-integer prescalers ones added FT232BM. allow addition subinteger prescalers used when aliasing Baud rate following ConfigData entry needed: [FtdiPort232.NT.HW.AddReg] 00,00,00,00,D0,80,00,00 (Note developer should paste above entry into FTDIPORT.INF, replacing original one) this case each field consists bytes, ordered follows: Byte0,Byte1,Byte2,Byte3. Bits through denote integer divisor while bits denote sub-integer divisor, follows 16,15,14 sub-integer divisor 16,15,14 sub-integer divisor 16,15,14 sub-integer divisor 0.25 16,15,14 sub-integer divisor 0.125 16,15,14 sub-integer divisor 0.375 16,15,14 sub-integer divisor 0.625 16,15,14 sub-integer divisor 0.75 16,15,14 sub-integer divisor 0.875 Note that this ConfigData entry same before except that each field consists bytes instead bytes. first highlighted byte ConfigData Flags byte format fields determined Bit4 Flags byte. example above, setting Flags byte means that Bit4 byte fields being used. divisor extracted each entry simple steps, shown here entry 35,40,01,00 Step re-order bytes: 35,40,01,00 00014035 Step extract sub-integer divisor; sub-integer 0.625 Step extract integer divisor: 13:0 0035 Step combine integer sub-integer divisors: 53.625 Step divide 3000000 divisor 3000000/53.625 55944 baud following lists standard values their respective baud rates. 10,27,00,00 divisor 10000, rate 88,13,00,00 divisor 5000, rate C4,09,00,00 divisor 2500, rate 1200 E2,04,00,00 divisor 1250, rate 2,400 71,02,00,00 divisor 625, rate 4,800 38,41,00,00 divisor 312.5, rate 9,600 9C,80,00,00 divisor 156, rate 19,230 4E,C0,00,00 divisor rate 38,461 34,00,00,00 divisor rate 57,692 1A,00,00,00 divisor rate 115,384 0D,00,00,00 divisor rate 230,769 06,40,00,00 divisor 6.5, rate 461,538 03,80,00,00 divisor 3.25, rate 923,076 00,00,00,00 RESERVED
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates D0,80,00,00 divisor 208.25, rate 14406 alias rate 920k baud standard baud menu option under windows: change 34,00,00,00 entry 03,80,00,00 (simple both values available from previous list) alias rate 197k baud standard 4,800 baud menu option under windows find best divisor, check that sufficiently accurate then modify appropriate file entry. 3000000/197,000 15.228. best divisor 15.25. 3000000/15.25 196,721. 196,721/197,000 99.8%. This well within required tolerance. bits 16:15:14 sub-integer divisor 0.25, lower bits replace 71,02,00,00 entry with 0F,80,00,00. Incorporating these changes FTDIPORT.INF entry becomes [FtdiPort232.NT.HW.AddReg] ,00,00,00,00,D0,80,00,00 This Windows 2000 changes should repeated Windows 98/ME entry also.
Future Technology Devices International Ltd. 2006
Revision History, Disclaimer, Contact Information
Revision History, Disclaimer, Contact Information
Document Revision History
AN232B-05 Version Initial document created March 2004. AN232B-05 Version Format updated, various corrections throughout.
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates
Disclaimer
Future Technology Devices International Limited 2006 Neither whole part information contained product described this manual, adapted reproduced material electronic form without prior written consent copyright holder. This product documentation supplied as-is basis warranty their suitability particular purpose either made implied. Future Technology Devices International Ltd. will accept claim damages howsoever arising result failure this product. Your statutory rights affected. This product variant intended medical appliance, device system which failure product might reasonably expected result personal injury. This document provides preliminary information that subject change without notice.
Future Technology Devices International Ltd. 2006
Revision History, Disclaimer, Contact Information
Contact Information
Head Office Glasgow, Future Technology Devices International Limited Scotland Street Glasgow United Kingdom Tel: 2777 Fax: 2758 E-Mail (Sales): sales1@ftdichip.com E-Mail (Support): support2@ftdichip.com E-Mail (General Enquiries): admin1@ftdichip.com Site URL: http://www.ftdichip.com Shop URL:
Branch Office Taiwan Future Technology Devices International Limited (Taiwan) 16-1, Sec. Mincyuan East Road Neihu District Taipei Taiwan Tel: +886 8791 3570 Fax: +886 8791 3576 E-Mail (Sales): tw.sales@ftdichip.com E-Mail (Support): tw.support@ftdichip.com E-Mail (General Enquiries): tw.admin@ftdichip.com Site URL: http://www.ftdichip.com
Branch Office Hillsboro, Oregon, Future Technology Devices International Limited (USA) 5285 Elam Young Parkway Suite B800 Hillsboro, 97124-6499 Tel: (503) 547-0988 Fax: (503) 547-0987 E-Mail (Sales): us.sales@ftdichip.com E-Mail (Support): us.support@ftdichip.com E-Mail (General Enquiries): us.admin@ftdichip.com Site URL: http://www.ftdichip.com
Agents Sales Representatives Please visit Sales Network page FTDI site contact details distributor(s) your country.
Future Technology Devices International Ltd. 2006
AN232B-05 Configuring FT232R, FT2232C FT232BM Baud Rates FT232BM FT232R FT8U232AM FTDIPORT.INF
Index
MBaud
-MMargin Error
MBaud
-NNon-Standard Baud Rate
-448 Clock
-RRevision History
-AAliasing
-SSpecial Case Divisors Standard Baud Rate Sub-Integer Divisor Sub-Integer Prescaler
-BBaud Rate Baud Rate Divisor
-VVCOMM
-CClock Port Port Library ConfigData Contact Information
-WWindows 2000 Windows Windows Windows
-DD2XX Device Manager Disclaimer Divisor
-FFT_SetBaudRate FT_SetDivisor FT2232C
Future Technology Devices International Ltd. 2006

Future Technology Devices International Ltd. 2006 AN232B-05 Confi

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