ST10F272B_12 STMICROELECTRONICS [STMicroelectronics], ST10F272B_12 Datasheet - Page 50

• Manufacturer Part Number: ST10F272B_12
• Description: 16-bit MCU with 256 Kbyte Flash memory and 12/20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Central processing unit (CPU)
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Figure 6.
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Central processing unit (CPU)
The CPU includes a 4-stage instruction pipeline, a 16-bit arithmetic and logic unit (ALU) and
dedicated SFRs. Additional hardware has been added for a separate multiply and divide
unit, a bit-mask generator and a barrel shifter.
Most of the ST10F272’s instructions can be executed in one instruction cycle which requires
31.25ns at 64 MHz CPU clock. For example, shift and rotate instructions are processed in
one instruction cycle independent of the number of bits to be shifted.
Multiple-cycle instructions have been optimized: branches are carried out in 2 cycles, 16 x
16-bit multiplication in 5 cycles and a 32/16-bit division in 10 cycles.
The jump cache reduces the execution time of repeatedly performed jumps in a loop, from
2 cycles to 1 cycle.
The CPU uses a bank of 16 word registers to run the current context. This bank of General
Purpose Registers (GPR) is physically stored within the on-chip Internal RAM (IRAM) area.
A Context Pointer (CP) register determines the base address of the active register bank to
be accessed by the CPU.
The number of register banks is only restricted by the available Internal RAM space. For
easy parameter passing, a register bank may overlap others.
A system stack of up to 2048 bytes is provided as a storage for temporary data. The system
stack is allocated in the on-chip RAM area, and it is accessed by the CPU via the stack
pointer (SP) register.
Two separate SFRs, STKOV and STKUN, are implicitly compared against the stack pointer
value upon each stack access for the detection of a stack overflow or underflow.
CPU block diagram (MAC Unit not included)
Doc ID 11917 Rev 3
ST10F272B/ST10F272E