AN910 Datasheet, PDF (14/51 Pages) STMicroelectronics – ST7 AND ST9 PERFORMANCE BENCHMARKING

ST7 AND ST9 PERFORMANCE BENCHMARKING
Table 3. High-end to low-end MCU strong and weak points (cont’d)
MCU
68HC11
(4 MHz)
68HC08
(8 MHz)
Strong points
instruction processing: 1-byte prefetch queue
fast 8-bit ALU:
8-bit datapath
625 ns 8x8 multiplication
special addr. modes: indexed with 8-bit offset or
post-increment
special instructions: memory-to-memory moves
compare & branch like
decrement & branch like
large memory space: up to 4 Mbytes with memory
expansion module
Weak points
instruction processing: standard (no prefetch)
medium 8/16-bit ALU: 2500 ns 8x8 multiplication
long average ICT:
1500 to 1750 ns
lacking instructions: 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
medium average ICT:
lacking addr. modes:
multitasking:
interrupt processing:
500 to 625 ns
no indirect addressing
no special capabilities
one interrupt at a time
recommended
no program priority register
hardware fixed priorities
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