Re: Virtual serial drive

[Michael J. Mahon <mjmahon@aol.com>]

BLuRry <brendan.robert@gmail.com> wrote:
> On Saturday, September 8, 2012 5:14:51 AM UTC-5, Riccardo wrote:
>> Ok, I restart to studied "Inside the Apple IIc" by Gary B. Little 1985,
>> Chapter 11, "The Serial Interface Ports", from page 299 to page 324,
>> it's the great work. And reopen my old book: "Sistemi a microprocessore"
>> by R. Baranzini, D. Capezzuto, G. Dugnani, HOEPLI 1986.
>> 
>> 
>> 
>> First:
>> 
>> - //c have two 6551 ACIA (Asynchronous Communication Interface Adapter)IC
>> 
>> - PC/MAC typical use Intel 8251A USART (Universal Synchronous Asynchronous             
>> 
>>   Receiver Transmitter)IC, i think.
>> 
>> 
>> 
>> both IC implement AIA RS-232-C and have two phases:
>> 
>>   
>> 
>>  Programmer and Communication
>> 
>>  
>> 
>> Right, my first question:
>> 
>> 
>> 
>>  At page 307 Figure 11-3 of "Inside the Apple IIc" book, show max set-up
>> speed to 19200 bit/s, but i great currently work up 115200 bit/s with ADTPro, Why ?
>> 
>>  
>> 
>> see you to next step.
>> 
>> 
>> 
>> Thanks
>> 
>> 
>> 
>> Riccardo
> 
> The reason why is that there is a different clock mode of the UART which
> lets it take its clock from a different source.  It just turns out by
> happy coincidence that this yields a mostly stable baud rate of  115.2k baud. :-)

Right--it just skips the clock prescaler. The baud rate is as stable as any
other. 

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon