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Link Port


The Link port is a 2.55 mm jack on the bottom of the calculator. This is the interface between the calculator and the outisde world. The TI-Graphlink, the Parallel Cable, and the Serial Cable all use the Link port to interface the calculator with a computer. You can also use a 2.5mm (male) <-> 3.5mm (female) converter and hook up the calculator to the headphones to play sound. My program, Sound Demo v1.0, takes advantage of this feature.

Much information was extracted from 86ports.txt (Alan Bailey), which was, in turn, extracted from ti-ports.txt (Dan Eble). Refer to these files for more detail.

Electrical Specifications of the Link Port

All data are transmitted in binary form - logical '1' or '0'
The TI-86 uses 'negative logic' which means that: 0 (0V) = active signal and 1 (5V) = not active signal. So if you measure the red and ground or the white and ground wires, it will measure 5V meaning the the link port is inactive. The red and white wires typically measures around 4.9V but on my multimeter I measured 5.5V (fresh batteries?). When I ran my Sound Demo program, I used my frequency counter and it fluctuated at around 1500 hz, varying 100's of hertz in both directions.

You can access the linkport with Port 7. Here are the specifications of Port 7:

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 stop 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

For more information on interfacing the link port with hardware, visit The TI-Electronics web site.

There are also some linkport routines by Randy Gluvna - linkport.h. I am not sure how to use these, however.