RE: TI-H: Clocking the link port


[Prev][Next][Index][Thread]

RE: TI-H: Clocking the link port



Yes it's true that the calc uses reverse logic for linking (0v = 1, 5v = 0).

This is basically how the TI-TI protocol works:

(active denotes a voltage of 0v ("on") )

Sending calc              | Receiving calc
--------------------------+---------------------------
                          | Waits until a wire is active,
                          | if both are active, jumps to
                          | Error Handler
                          |
Sends the first bit:      |
1 : Red wire is active,   |
    White is inactive     |
0 : White wire is active, |
    Red wire is inactive  |
                          |
                          | Activates the wire that is 
                          | inactive and records the 
                          | bit it received (both wires
                          | are now active)
                          |
Waits until both wires    |
are active, then makes    |
both inactive (but one is |
still active from the     |
receiving calc)           |
                          |
                          | Waits for only one to be
                          | active (the one it
                          | activated), then makes both
                          | inactive.
                          |
Waits until both wires    |
are inactive, then        |
repeats 7 more times (for |
a byte)                   |

Everytime either calc waits, it is in a loop.  Usually it checks for the stop
condition twice per loop.  Everytime the loop completes, it decrements de
(which is initially set to $FFFF).  When de is 0, it jumps to the Error
Handler (this is a timeout).


At 09:57 PM 9/2/97 -0800, Jan Zumwalt wrote:
>Let me add another question too. I heard that the calc uses Ov for a mark
>and 5v for a zero. Is this true?
>
>>The calc to calc protocol is asynchronous, as are all the homemade 
>>link
>>cables.  The official GraphLink converts the TI protocol to 9600 baud.
>>--
>>Brian Leech
>>butvis@mindspring.com
>>ICQ UIN: 1355611
>
>Okay, so now I'm lost.  How do the calcs know when a bit is ready to be
>read from the link.  Maybe I should start at the begining, can someone
>explain how linking works from a hardware perspective?

--
Brian Leech
butvis@mindspring.com
ICQ UIN: 1355611




References: