Manual

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

ALE

PSEN

AD0-7

ADDRESS A15-A8 PORT2

SINGLE CYCLE

*Shaded areas are held in a weak latch on the

ort until overdriven.