Maxim Integrated High-Speed Microcontroller - Manual (Page 66)

High-Speed Microcontroller User’s Guide
Rev: 062210 66 of 176
One other type of two-cycle instruction requires two cycles but only includes one byte. This is because
the second memory access is the result of the instruction. These are the MOVX instructions. An example
is as follows:
MOVX @DPTR,A F0h
The second cycle in this instruction is the write to data memory at the address pointed to by the data
pointer. Thus this instruction is a two-cycle one-byte instruction, but requires two memory accesses. The
MOVX timing is a special case, since the user can control it with the Stretch MOVX feature. The timing
for the Stretch MOVX is discussed in Section
6 : Memory Access
.
Figure 5-3. Single-Cycle Instruction Timing
RETURN DATA
D7-0
CLK
C3 C1 C2 C4
ALE
PSEN
AD0-7
ADDRESS A15-A8 PORT2
SINGLE CYCLE
*Shaded areas are held in a weak latch on the port until overdriven.