[AABB] = pointer to source data
[CCDD] = pointer to target
[EE]   = number of bytes to copy

memory
$D367 = >$7F (i.e. bit 7 set) (IF USING 10F, S+Q need not apply)
$D369 = $FA

using north connection
$D371 = non-$FF, preferably same as mapID
$D372 = [BB]
$D373 = [AA]
$D374 = [DD]
$D375 = [CC]
$D376 = [EE]
$D377 = $00

using south connection
$D37C = non-$FF, preferably same as mapID
$D37D = [BB]
$D37E = [AA]
$D37F = [DD]
$D380 = [CC]
$D381 = [EE]
$D382 = $00

use 10F to do the copy, or S+Q
note that 10F can stack overflow so S+Q every x times (todo what is x)