PIC24H单片机讲解(1).ppt

PIC24H系列单片机体系结构及外设模块讲解 主讲人：胡洲 时 间：2011-7-14 Register Introduce (1) Register Introduce (2) Software stack pointer W14 Software Stack Frame Pointer A frame is a user-defined section of memory in the stack used by a single subroutine. W14 is a special working register because it can be used as a Stack Frame Pointer with the LNK (link) and ULNK (unlink) instructions. W14 can be used in a normal working register by instructions when it is not used as a Stack Frame Pointer. Stack Pointer Overflow The stack overflow check is not enabled until a word write to SPLIM occurs, after which time it can only be disabled by a device Reset. If the contents of W15 are greater than the contents of the SPLIM register by 2, and a CALL instruction is executed or an interrupt occurs, a stack error trap is generated. SR: CPU Status Register DC: MCU ALU Half Carry/Borrow bit IPL2:0: CPU Interrupt Priority Level Status bits N: MCU ALU Negative bit OV: MCU ALU Overflow bit Z: MCU ALU Zero bit C: MCU ALU Carry/Borrow bit CORCON: Core Control Register IPL3: CPU Interrupt Priority Level Status bit PSV: Program Space Visibility in Data Space Enable bit Note 1: User interrupts are disabled when IPL3 = 1. Data Memory(1) The size of the X data space is device specific. DMA RAM is not available on all devices. Near data memory can be accessed directly via file register instructions that encode a 13-bitaddress into the opcode. All data memory can be accessed indirectly via W registers or directly using the MOV instruction. Data Memory(2) Upper half of data memory map can be mapped into a segment of program memory space for Program Space Visibility (PSV). Data Alignment Program Memory Map(1) The address boundaries for user Flash program memory will depend on the device variant selected. Program Memory Map(2) Device Configuration Registers Instruction Fetch Example Using Table instructions(1) Using Table instructions(2) Program Space Visibility Program Space Visibility Example 1 Compiler Mana