Differences between the 150 and 150S

For Christmas 1996, Timex introduced a smaller version of the 150 called the 150s.  This watch has substantially the same hardware and capabilities as the 150, but in a smaller package.  You can tell the difference between the two by entering COMM Mode.  If the version on the bottom line is V2.0, then the watch is a 150.  If it says V2.1, it is a 150S.  There is also a newer release of the Datalink software (V2.1) for the 150s which works with all of the Datalink watches.  The older V2.0 software will not talk to the 150s.

It is not possible to run the same wristapp on both watches because of a few differences:

• The addresses for the display segments have changed. Mostly this has been a simple subtraction of 2 from the offsets for addressing the display segments, but it also involved the shuffling of a couple of the pixels in the segments on the bottom line. Since turning on a segment is a hard coded constant, an application has to be recompiled for the different display.
• To accomodate the change in display segments, a couple of ROM routines have been changed.  This resulted in a shuffling of the addresses of a number of routines within the watch.
• To further complicate things, the order of a few routines in the ROM has been changed.  While the routines are exactly the same in both the 150 and the 150s, the location of these routines is never the same.
• The CPACKET_START packet has a 4 for the version code instead of a 3.
• Even with all this shuffling, the memory map for the low ram appears to be exactly identical, as does the actual 6805 hardware.

Dealing with the Differences

Because the two watches are so different, you have to essentially write the same program twice with different targets for all of the system routines and any segment poking that is done.  The V2.1 software handles this by storing both copies of the code in the .ZAP file with a description field to identify which watch the software is targeted to.  When you identify the type of the watch to the datalink software, it automatically chooses the right software to send.