Seems like it's time to cook up the documentation, because my minecartputer is now officially functional. It has, in one unbroken no-errors process, sorted three data by size. The program consists entirely of comparisons, reads, writes, and a few jumps. The major point is that my ROM bank has passed the test: the active program memory consists of a whopping eight six-bit words. Now you can't do much programming with eight instructions (the sorting program takes up 22 commands), so...
just read further program modules from a larger "memory store". It's adressable, compact, and takes fewer mechanisms to run than it holds bits because the information is not held by active/inactive signals, but rather by "stored" minecarts which are decoded and the resultant signals sent to the active program storage by a single array shared by the sixteen modules.
The sorting program consists of three modules and is in fact accessed from a "boot module" which shall in future allow choosing between several programs.
Module 2
111 010 div. read datum from tape (to buffer)
001 001 write buffer to Reg. A
111 010 div. read next datum from tape
001 010 write buffer to Reg. B
111 010 div. read next datum from tape
001 011 write buffer to Reg. C
110 010 load Module Nr. 3
xxx xxx unused
Module 3
100 011 test A>B, skip next if not
101 101 jump to pos. 6
100 000 test B>C, skip next if not
110 011 load Module 4
111 110 Halt (A</=B</=C, list sorted)
000 010 read Reg. B (to buffer)
010 100 add. A+0, write to B (copy Reg. A to Reg. B)
001 001 write buffer to Reg. A #operation loops back to command Nr. 1
Module 4
000 011 read Reg. C (to buffer)
001 110 write buffer to Reg. F
000 010 read Reg. B (to buffer)
001 011 write buffer to Reg. C
000 110 read Reg. F
001 010 write buffer to Reg. B
110 010 load Modul 3
xxx xxx unused
Data were not entered into the registers directly, but loaded from a single-use one-direction tape. Data provided:
1 011 101 001 (745)
0 011 011 100 (220)
0 010 111 000 (184)
so the program had to completely turn the order around. Which it did.