[aprssig] Re: MFJ 1270B

Ron Stordahl ron.stordahl at digikey.com
Sun Jan 1 09:41:39 EST 2006

Fred Atkinson, WB4AEJ wrote:

>>1)   At some point, MFJ dropped KISS support to make room for other
>>features in their firmware -- not certain when they started
>>non-supporting it.  Test it in KISS mode and see if it works.
>    Not sure how to do that.  Haven't found documentation on the current
>commands anywhere as yet.  But according to the manual (the 1270C manual, I
>couldn't find the one for the 1270B), it does indeed support KISS mode.

Some time ago when I discovered that the latest MFJ1270C's no longer 
supported KISS I contacted MFJ and this was confirmed.  I jokingly said 
that I was sure they would reflect this change in a revision to the 
manual!  What actually happened is they discontinued the product 
entirely.  Although it was a reliable product, I have a dozen of them in 
remote service, it was obviously too expensive to manufacture.  Very old 

As to KISS, the best solution by far is to replace the eprom with a 
JKISS eprom.  Works perfectly with AGWPE or the new AGWtoBPQ, and thus 
UIView32.   The JKISS image is burned without any user configuration.  
The JKISS image is in the bpq408a.zip package 
http://www.dxspots.com/bpq32/bpq408a.zip  With JKISS there are no 
options to set ever, you just turn it on!

As to testing KISS, there is a simple test program, TXTest, at 
.http://www.tnc-x.com/documentation.htm   I tried it with JKISS just for 
fun and it works, however if the LED's on the 1270B/C blink 3 times upon 
power up it's nearly a certainty that the software is just fine.

>>The original TNC2 design (of which the MFJ is a near clone) used two 8K
>>static RAMS and a 27128 EPROM. These three chips filled all three
>>sockets.  The board layout provided support for anticipated  future
>>higher density stat RAMS.   A movable jumper on the board provided for
>>addressing two 8K RAMS or a single (at the time horribly expensive) 32K
>>Within a few years the single 32K RAM became standard, the jumper was
>>bridged with a PC board trace that had to be slashed with an X-acto
>>knife if you  wanted to downgrade to the dual 8K configuration, and the
>>second socket has remained empty ever since.
>>There is no point in adding memory; indeed you CAN'T add memory.  This
>>thing is NOT a PC capable of addressing hundreds of megabytes of RAM.
>>The entire memory address space of the Z-80 CPU in the TNC is only 64K!!
>>   The 32K RAM occupies half of the memory space; the firmware in the
>>27256 (32K  bytes) EPROM already occupies the other half.   The entire
>>TNC firmware is hand-coded directly in Z-80 assembly code and takes a
>>fraction of the RAM and ROM that typical PC apps take.    

>    According to the manual, memory can be increased to 512 kilobytes.  I'm
>still trying to find the specifics on the type of memory required.

With KISS (or JKISS) there is no need whatsoever to add more memory!  It 
wouldn't (couldn't) even be used.

Ron Stordahl, N5IN

>Fred, WB4AEJ

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