[TI-H] Re: Low Level Link Port Programming


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[TI-H] Re: Low Level Link Port Programming




>The TI link protocol uses two wires (for data, obviously three are needed
>with ground) in order to avoid having the protocol depend on timing (think
>about how it would have to work with only one wire).  The TI link protocol
>is decent, and probably the easiest way to interface with the calculator.
>Once you get the concepts down, it's fairly easy to work with.  If you
don't
>have the luxury of controlling the protocol of your other device, then of
>course this doesn't apply.
>
>The text below is from the ports section of the Assembly Studio 8x help
file
>(an excellent source for info on all z80 calculators):

Isn't the ASMstudio8x officially for the TI-86? The link port is 00h for 83+
calcs.

>--- Paste starts here ---
>
>Port 7 - Link port control
>
>This port is used to read or set the state of the two link port wires.
>
>Write: 11....00
>
>Bits 2 & 4 - 1: makes red wire inactive
>  0: makes red wire possibly active if other calc says so
> Bits 3 & 5 - 1: makes white wire inactive
>  0: makes white wire possibly active if other calc says so
>
>Read: 0000....
>
>Bit 3 - 1: white wire current stopped because this calc said so
>  0: white wire possibly active
> Bit 2 - 1: red wire current stopped because this calc said so
>  0: red wire possibly active
> Bit 1 - 1: white wire active
>  0: white wire inactive
> Bit 0 - 1: red wire active
>  0: red wire inactive
>
>Examples:
>
>To turn on certain wires, do the following:
> ld a,%11010100 ;White wire ON
> out (7),a
> ld a,%11000000 ;White wire ON, Red wire ON
> out (7),a
> ld a,%11101000 ;Red wire ON
> out (7),a
> ld a,%11111100 ;nothing ON
> out (7),a
>
>To check if certain wires are turned on, do the following:
> in a,(7)
> and %00000011 ;only the lower two bits matter
> cp 3 ;Bits 0 and 1 set
> jr z,BothActive
> cp 2
> jr z,WhiteActive ;Bit 1 set
> cp 1
> jr z,RedActive ;Bit 0 set
>
>cp 0
> jr z,NoneActive ;Neither bits set
>
>See the file Link86.asm in the Samples folder for an example routine to
send
>and receive bytes through the link port.
>
>--- Paste ends here ---
>
>> Which apparently outputs a 1 and 0.  However, this would only use one
line
>if
>> I am correct.  I am trying to interface to a device without using TI's
>> standard link-port protocol.
>
>
>
>