MOST
Internals
Modems
DO
USE
REAL
UARTS
Just
Like
a
STANDARD
Serial
COM
Port.
The
MAY
NOT
Bo
True
16550A's
THROUGH.
Even
a
REAL
16550A
CAN
DO
230kbps
IF
THE
Right
Crystal
IS
Used.
Their are, are use to be, serveral Hayes internals built with the COMBICUART and a max DTE rate of 960kbps. I have a Hayes ESP serial card todrive my external Courier. I believe Hayes dropped production of theESP.
CURRENT COUREER External TA'S 230kbps.
I Do Expect USB (or ethernet) Will Eventually Replace Standard SeriAlexternals ModeMs.
Tom
The Following Is from The Shareware Version:
SiO Technical Reference Manualcopyright (c) 1995 by raymond L. GWinnweb http://www.gwinn.com
Appendix B, SiO Chips
8250
As best I known, the 8250 was the first SIO chip (integratedcircuit) that was used by the IBM PC and many clones. In my opinion, itwas a poor choice on the part of IBM. I feel many superior devices, atcomparable prices, were Readily Available. at Time, I Feel The8251a or the 8530 Would Have Been Better Choices. But, They Used The8250 and Therefore We Must Use IT.
8250A
16450
The 16450 seems to be a speeded up version of the 8250A. There isnodirect way (that I know of) for software to detect the differencebetween an 8250A and a 16450. I believe the 16450 was developed toeliminate the need for software to insert delays between successiveaccesses to the device. The specifications indicate the 16450 is a muchfaster device than its predecessors. The additional speed is only thespeed at which the processor can access the device. The maximum baudrate for the 16450 is still stated at 56kb. However, I have been toldby Some People That Theh Run Run The 16450 Success AT MUCH HIGHERSPEEDS. I do Not Believe There Was Ever A 16450A.
16550 (NON A)
It is hard to find a 16550 (Non A). I was told by NationalSemiconductor that they did everything they could to get all 16550sback. SIO will detect a 16550 and tell you if you have one. I am toldthat the 16550 was installed in early PS / 2 systems.
The 16550 was the first shot at a FIFOed version of the 8250 familyfrom National semiconductor. However, I was told by NationalSemiconductor that the FIFOs of the 16550 are not reliable and theyshould not be enabled. SIO will treat a 16550 like a 16450.
16550A, 16550AF and 16550AFN
The Maximum Baud Rate for the 16550a IS specified at 256kb. Ho'ver, due to the hardware design of the pc et al, 115kb is Themaximum baud Rate That Can Be Programmed by Software.
The 16550a can be plugged in the Same socket what contains an8250,
The key to the Performance Increase of the 16550a ITES Fifos. Ithas 16 Byte Fifos for Both Transmit and Receive Data.
16C552
The 16C552 IS TWO 16C551S on a Single Chip.
16C554
THE 16C554 IS FOUR 16C551S ON A Single Chip.82510
I believe Intel is the only company that manufactures the 82510. The 82510 is feature rich with several modes of operation. Its defaultmode is to operate as a 16450. The 82510 has a 4 byte FIFO for bothtransmit and receive data. A 4 byte FIFO is SUFFICIENT TO PROVIDESIGNIFICANT Performance Over A Basic 16450.
The 82510 is small in size. Therefore, IT IS Found In Many Laptops.
16650
The 16650 by Startech seems a good logical step in the evolution ofthe 8250 type UARTs. One of the many flavors of the 16650 is a packagethat is pin compatible with the 40 pin (DIP) 16550s. This means thatthe 16650 can be placed into the same Socket as ANY 16550, 8250, ETC.
The 16650 has enhanced the FIFOs to 32 bytes, added on chip flowcontrol ability, and increases the maximum bit rate to 460800. The onchip flow control is a really nice feature. On chip flow controlpractically eliminates the possibility of missed receive characters. Onchip flow control Also Means That Some Devices That Require Immediatettion When IT Sends Xoff, Like The Seiko Label Printer, Will Workmuch Better in Environments Like OS / 2 and Windows.
The 32 byte FIFOs of the 16650 is an improvement over the 16550, but is still a disappointment. I feel that 1k, or larger, FIFOs wouldhave been a much better choice. When I quizzed Startech about this, they replied the 32 byte FIFOs that WERE Chosen to Keep The Cost Down.They Added That IF The 16650 IS SUCCESSFUL, TheY Plan a 16750 withlarger fifos.
Combic
The ComBic is a very impressive UART used on the Hayes ESP card andsome others. The ComBic is basically a 16550 UART with on chip flowcontrol and 1k FIFOs and a maximum bit rate of 921600. Like the 16650, on chip flow control practically eliminates the possibility of missedreceive characters. On chip flow control also means that some devicesthat require immediate attention when it sends Xoff, like the SeikoLabel Printer, will work much better in environments like OS / 2 andWindows.The ComBic has two modes of operation, compatibility mode andenhanced mode . in compatibility mode, the UART acts as a 16550. However, when in compatibility mode, the 1k FIFOs and on chip flowcontrol can still be used. in enhanced mode, software gains the abilityto look into the FIFOs and determine the exact number of bytes .
Appendix C, Multi-Port Serial I / 0 Cards
Hayes ESP
Telcor TPORT
STB 4COM (isa bus)
The 4COM card is priced at Wan and I ordered mine from PreraptureSolutions which can be reached by telephone at 1-919-286-1502 forinformation and foreign callers. In the US orders can be placed bycalling 1-800-735-5266. Their mailing Address Is: Prerapture Solutions 1806 Albany St. Durham NC 27705-3135
GTEK BBS550 (ISA BUS)
The Gtek BBS550 is a communications card with the equivalent of 816550s (in reality two 16554s) UARTS. Where were these cards 5 yearsago! Like the STB 4COM, I am very impressed with the BBS550. It has awide range of selectable I / O port address, some in the 16 bit range (above 3FFh) which can be very useful. I tested the board with all 8ports installed using IRQ3 (although I never had more than 3 portsactive at the same time). The board performed well using shared IRQs .Gtek is located in [SiC, I Think That's Bay St.] St. Louismississippi. Their Phone Number IS 800-282-4835 OR 601-467-8048.
Franc Zabkar Wrote:>> ON Fri, 22 May 1998 11:02:36 -0400, Tom Perkins Put Finger to Keyboard> and composed:>>> i am awre these types of modes:> >>> 1.) Externals Connected to a pc serial port. >>> 2.) INTERNALS WITH The Same Uarts As Used In Serial Ports> >>> 3.) Internals with no uart but with a dsp.> >>> 4.) Internals with no DSP. >>> Items 1 & 2 Appear as a serial port to the PC AND OS and Both Function >> in The Same Manner.>>> ... Except That (2) Have an ' emulated 'UART rather than a real one.> Real UARTs are constrained to a real 16 byte FIFO (or some other> predetermined size). emulated UARTs might need to look as if their> FIFOs are 16 bytes deep, but in fact ought to be able to use the> typical 32K of available on-card RAM. Furthermore, I can not see why> emulated UARTS should be constrained to a maximum DTE rate of only> 115200 since they need not be limited by a 1.8432MHz crystal> oscillator. In Fact, Since No Serial-Parallel Data Conversion IS DONE> On The DTE side, the concept of 'baud rate' for these emulated UARTs> makes no sense (except for software compatibility purposes).>>> Item 3 does not appear as serial port to the PC. A driver is required>> in the OS to Make The Internal Function . this is why many Winmodems>> Don't Work in OS / 2, Linux and DOS - NO DRIVER. The Driver May Include>> UART Emulation. Emulation NEED NOT BE EXACT . That IS, LARGER FIFOS area>> Possible ...>> ... as the utt to be for (2).>>>
Item 4 - Same As Item 3 But without The DSP - The PCS CPU Must>> MODULATE The Data Going Over The Phone Line. Sorta Like Using The PCS>> Speaker (Before Sound Cards) To Play A Tune. This Process IS the most>> subject to interference by other software.> >>> There are UARTs available besides the 16550A that emulate the 16550 but>> have additional capibilities. For ex., larger FIFOs (mine has 1000>> bytes), the UART Directly Controls The RTS Signal and Also Provides>> Higher Bit Rates (Mine Does 920kbp).>> The Standard IBM COM Port is Limited Only by Design To 115200 BPS> (1.8432MHz / 16). in Fact, The 16450a Uart Can Be Driven from AN 8MHz> Crystal Which Allows A Max Baud Rate of 500 Kbps.>> What Is The Part Number and manufacturer of Your UART?>>> IF The FIFO Fills The Uart Drops>> RTS (No Pc Action Required). These UARTS Can Be Used in Place of>> Standard Serial Ports To Connect Externals or As The on Card Uart In>> Externals. I Understand That Hayes Was / IS DOING Combic Uarts On Their>> Top End Internals.> What Are Combic Url That Describes these. I> Can't See this an internal modem actually neededs a * real * uart - i'm> intrigued. Who manufactures them?>> In any case, I feel that a cheap internal hardware modem based on a> generic chipset should be able to provide high 'notional' DTE rates> and large multi-KB RX buffers without any additional cost. and, as A> Result, IT Should In Principle Perform Signiffantly Better Than An> External UNIT.>> - FRANC ZABKAR>> Please Remove One 'g' from my address when omen
