AN910 Datasheet, PDF (34/51 Pages) STMicroelectronics – ST7 AND ST9 PERFORMANCE BENCHMARKING

ST7 AND ST9 PERFORMANCE BENCHMARKING
7.3.7 68HC11 MCU core
Programming model
Accumulators
- two 8-bit accumulators
useable as one 16-bit accumulator
- two 16-bit index registers
- other registers
16-bit program counter
16-bit stack pointer
condition code register
LDAA #8, X
ADDB #A0
Instruction set
Cisc encoding
- CPI
2 cycles to 41 cycles
- average CPI
between 6 and 7 cycles
- IL
1 byte to 3 bytes
- average IL
between 2 and 3 bytes
- special instructions
exchange register contents
68HC11 CPU
Cpu internal buses
16-bit address bus, 8-bit data bus
(to be confirmed)
Instruction processing
Standard
- sequential processing
Arithmetic Logic Unit
+/x
8-bit datapath
- 8/16-bit operations
- special functions
8x8 unsigned multiplication
10 cycles
16/16 unsigned integer division 41 cycles
16/16 unsigned fractional division 41 cycles
On-chip/Off-chip buses
- on-chip buses
16-bit address bus
8-bit data/program memory bus
- off-chip buses
8/16-bit address bus
8-bit data/program memory bus
the two buses are multiplexed with ports
Memory Space
Von Neumann organization
- linear data/program memory space
64 kbytes
256-byte zero page
64-byte peripheral register space
upper 41-byte interrupt vector table 18 interrupts
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