[Coco] I am looking for a few Code Snippets for the CoCo's.

[Dave Philipsen]

I'm not familiar with the Apple Super Serial card but likely it used a UART as did the serial ports on the IBM PCs.  This is way better than the 'bit-banger' port on the CoCo because the UART takes care of the precise bit timing, buffering, error detection, framing, and assembling of the bitstream in the serial communications.  With the onboard serial port the 6809 must do all of that and it becomes quite a chore when you're working at bit rates above 9600.

Just as a SAM/GIME chip handles all of the video timings necessary for the CoCo that a 6809 could never do on its own, so too, a UART can handle a chore which becomes too tedious for the 6809 at anything more than the slower bitrates.

With dedicated UART/USART hardware you can free up a whole bunch of CPU time that could be well spent elsewhere.  I have a custom 6809-based FPGA design with a 250kbps USART, and three 115.2kbps UARTs and it can handle simultaneous communications over all four of them with ease even when the CPU core is slowed down to 1 MHz.

Dave

> On Mar 17, 2017, at 3:51 PM, Mark D. Overholser <marko555.os2 at gmail.com> wrote:
> 
>> On 17-Mar-17 12:57, Salvador Garcia via Coco wrote:
>> Hi all, this got my attention and sparked my curiosity. Allen
>> mentioned that reading the bit banger port required assembly. Does
>> that mean that if I connect a serial device, such as a scale, to the
>> bit banger, I can't have a typical BASIC program to read the
>> information coming from the external device? Thanks! Salvador
>> 
> 
> 
> 
> My understanding of the CoCo's Bit-Banger Port is that it functions like the Apple ][ Super Serial Card ( SSC ) or the original IBM PC's Serial Port...
> 
> Output mainly, with Polled Input, ( verses Interrupt Driven )
> 
> You need an Assembly Language "driver" to setup your incoming and outgoing buffers and the Interrupt Service Handler ( ISR ) to "fetch" the incoming Bytes and Queue them...
> 
> 
> Does anyone know if the CoCo RS-232 Cartridge, which has a Terminal in ROM, can be used by a BASIC or Assembly Language program, at least the Low Level Routines???
> 
> 
> Many years ago I wrote a Serial Terminal Program for the IBM PC/AT in Turbo C 2.00, using a book by Al Stephens, IIRC, with Lots of Assistance from the "C. Programmer's Guide to Serial Communications" by Joe Campbell..
> 
> I have not attempted the same with the Apple ][ or CoCo..  But I am Willing to Learn....
> 
> 
> I have also done this kind of thing on Microchip PIC Processors too...
> 
> 
> <https://www.amazon.com/C-Programmers-Guide-Serial-Communications/dp/0672225840>
> 
> 
> MarkO
> 
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