DS80C320 Datasheet, PDF (7/42 Pages) Dallas Semiconductor – High-Speed/Low-Power Micro

DS80C320/DS80C323
HIGH-SPEED OPERATION
The DS80C320/DS80C323 is built around a high speed 80C32 compatible core. Higher speed comes not
just from increasing the clock frequency, but from a newer, more efficient design.
In this updated core, dummy memory cycles have been eliminated. In a conventional 80C32, machine
cycles are generated by dividing the clock frequency by 12. In the DS80C320/DS80C323, the same
machine cycle is performed in 4 clocks. Thus the fastest instruction, one machine cycle, is executed three
times faster for the same crystal frequency. Note that these are identical instructions. A comparison of the
timing differences is shown in Figure 2. The majority of instructions will see the full 3 to 1 speed
improvement. Some instructions will get between 1.5 and 2.4 X improvement. Note that all instructions
are faster than the original 80C51. Table 2 below shows a summary of the instruction set including the
speed.
The numerical average of all opcodes is approximately a 2.5 to 1 speed improvement. Individual
programs will be affected differently, depending on the actual instructions used. Speed-sensitive
applications would make the most use of instructions that are three times faster. However, the sheer
number of 3 to 1 improved opcodes makes dramatic speed improvements likely for any code. The Dual
Data Pointer feature also allows the user to eliminate wasted instructions when moving blocks of
memory.
INSTRUCTION SET SUMMARY
All instructions in the DS80C320/DS80C323 perform the same functions as their 80C32 counterparts.
Their effect on bits, flags, and other status functions is identical. However, the timing of each instruction
is different. This applies both in absolute and relative number of clocks.
For absolute timing of real-time events, the timing of software loops will need to be calculated using the
table below. However, counter/timers default to run at the older 12 clocks per increment. Therefore, while
software runs at higher speed, timer-based events need no modification to operate as before. Timers can
be set to run at 4 clocks per increment cycle to take advantage of higher speed operation.
The relative time of two instructions might be different in the new architecture than it was previously. For
example, in the original architecture, the “MOVX A, @DPTR” instruction and the “MOV direct, direct”
instruction used two machine cycles or 24 oscillator cycles. Therefore, they required the same amount of
time. In the DS80C320/DS80C323, the MOVX instruction can be done in two machine cycles or eight
oscillator cycles but the “MOV direct, direct” uses three machine cycles or 12 oscillator cycles. While
both are faster than their original counterparts, they now have different execution times from each other.
This is because in most cases, the DS80C320/DS80C323 uses one cycle for each byte. The user
concerned with precise program timing should examine the timing of each instruction for familiarity with
the changes. Note that a machine cycle now requires just four clocks, and provides one ALE pulse per
cycle. Many instructions require only one cycle, but some require five. In the original architecture, all
were one or two cycles except for MUL and DIV.
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