AN910 Datasheet, PDF (13/51 Pages) STMicroelectronics – ST7 AND ST9 PERFORMANCE BENCHMARKING

ST7 AND ST9 PERFORMANCE BENCHMARKING
Table 3. High-end to low-end MCU strong and weak points
MCU
Strong points
Weak points
80C51XA
(20 MHz)
instruction processing: 7-byte prefetch queue
predecoding
fast 8/16-bit ALU:
16-bit datapath
600 ns 8x8 multiplication
short average ICT:
250 to 300 ns
special addr. modes: indirect with 8/16 offset or
auto-increment
special instructions: compare & branch like
decrement & branch like
memory-to-memory moves
multitasking:
context switching capabilities
large memory space: up to 16 Mbytes
interrupt processing: nested mode
4-bit program priority register
programmable priority levels
address alignment:
lacking addr. modes:
even jump/branch address
even word operand address
NOP instructions in assembly
code
no indexed addressing
68HC16
(16 MHz)
instruction processing: 3-stage prefetch queue
predecoding
fast 8/16/32-bit ALU: 16-bit datapath
625 ns 8x8 multiplication
short average ICT:
375 to 440 ns
special addr. modes: post-modified indexed
with 8-bitoffset
special instructions: memory-to-memory moves
multitasking:
context switching capabilities
large memory space: up to 1 Mbyte
up to 16 Mbytes with memory
expansion module
interrupt processing: nested mode
3-bit program priority register
programmable priority levels
address alignment:
instruction lengths:
lacking addr. modes:
lacking instructions:
performance penalty if odd
word operand addresses
only even
no direct addressing
index register manipulation
compare & branch like
decrement & branch like
68HC12
(8 MHz)
instruction processing: 2-stage prefetch queue
predecoding
fast 8/16-bit ALU:
20-bit datapath
375 ns 8x8 multiplication
short average ICT:
375 to 500 ns
special addr. modes: auto-incr/decrement indexed
accumulator offset indexed
special instructions: memory-to-memory moves
incr/decrement & branch like
test & branch like
large memory space: up to 4 Mbytes with memory
expansion module
multitasking:
interrupt processing:
need memory expansion
module
one interrupt at a time
recommended
no program priority register
hardware fixed priorities
instruction encoding:
short average IL:
special addr. modes:
special instructions:
H8/300
(10 MHz)
risc-like encoding
2 to 3 bytes
register indirect, 16-bit offset
or pre/post-increment
block moves
instruction processing: standard (no prefetch)
medium 8/16-bit ALU: 1400 ns 8x8 multiplication
medium average ICT: 500 to 600 ns
lacking instructions: 16-bit shifts/rotations
compare & branch like
decrement & branch like
multitasking:
no special capabilities
memory space:
64 kbytes
interrupt processing: one interrupt at a time
recommended
no program priority register
hardware fixed priorities
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