精品-MSP430单片机课件.ppt

* Copyright 2009 Texas Instruments All Rights Reserved www.msp430.ubi.pt Organization of the MSP430X CPU: Although the MSP430X CPU structure is similar to that of the MSP430 CPU, there are some differences that will now be highlighted; With the exception of the status register SR, all MSP430X registers are 20 bits; The CPU can now process 20-bit or 16-bit data. Central Processing Unit (MSP430X CPU) (2/10) * Copyright 2009 Texas Instruments All Rights Reserved www.msp430.ubi.pt Central Processing Unit (MSP430X CPU) (3/10) The MSP430X CPU has 16 registers, some of which have special use: R0 (PC) Program Counter: Has the same function as the MSP430 CPU, although now it has 20 bits. R1 (SP) Stack Pointer: Has the same function as the MSP430 CPU, although now it has 20 bits. R2 (SR) Status Register: Has the same function as the MSP430 CPU, but it still has 16 bits. * Copyright 2009 Texas Instruments All Rights Reserved www.msp430.ubi.pt Central Processing Unit (MSP430X CPU) (4/10) R2 (SR) Status Register: Description of the SR bits: * Copyright 2009 Texas Instruments All Rights Reserved www.msp430.ubi.pt Central Processing Unit (MSP430X CPU) (5/10) R2 (SR/CG1) and R3 (CG2) Constant Generators: Registers R2 and R3 can be used to generate six different constants commonly used in programming, without adding an additional 16-bit word to the instruction; The constants are fixed and are selected by the (As) bits of the instruction. (As) selects the addressing mode. Values of constants generated: * Copyright 2009 Texas Instruments All Rights Reserved www.msp430.ubi.pt Central Processing Unit (MSP430X CPU) (6/10) R2 (SR/CG1) and R3 (CG2) Constant Generators: Whenever the operand is one of the six constants, the registers are selected automatically; Therefore, when used in constant mode, registers R2 and R3 cannot be used as source registers. R4-R15 – General-purpose registers: Have the same function as in the MSP430 CPU, although they now have