Reading the datasheet for the 4514 tells me that it is a latch/decoder. The datasheet tells me the latch will hold the data input presented to it before the '1' to '0' transition of the strobe signal.

Therefore to update the 4514:

;assume strobe is '0'
; A has the value 0..15 to output to the 4514
mov c,a.0
mov p0.0,c
mov c,a.1
mov p0.1,c
mov c,a.2
mov p0.2,c
mov c,a.3
mov p0.3,c ;copy the lower 4 bits to the output port
setb strobe
clr strobe ;update the 4514 latch
; job done