Maxim-integrated MAX31782 Manual de usuario descargar pdf (Pagina 10)

Maxim Integrated 2-6

MAX31782 User’s Guide

Revision 0; 8/11

2.4.1 Program Memory Access

The instructions that the MAX31782 is executing reside in what is defined as the program memory. The MMU fetches

the instructions using the program bus. The instruction pointer (IP) register designates the program memory address of

the next instruction to fetch. The IP register is read/write accessible by the user software. A write to the IP register forces

program flow to the new address on the next cycle following the write. The content of the IP register is incremented

by 1 automatically after each fetch operation. From an implementation perspective, system interrupts and branching

instructions simply change the contents of the IP register and force the op code to fetch from a new program location.

2.4.2 Program Memory Mapping

The MAX31782’s mapping of the three memory segments (flash, SRAM, and utility ROM) as program memory is shown

in Figure 2-2

. The mapping of memory segments into program space is always the same. When referring to memory

as program memory, all addresses are given as word addresses. The 32KWord flash memory segment is located at

memory location 0000h through 7FFFh and is logically divided into two pages, each containing 16KWords. The utility

ROM is located from location 8000h through 8FFFh, followed by the SRAM memory segment at location A000h through

A3FFh. The user code reset vector, which is the first instruction of user program code that is executed, is located at

flash memory address 0000h. User program code should always begin at this address.

2.4.3 Data Memory Access

Data memory mapping and access control are handled by the memory management unit (MMU). Read/write access

to data memory can be in word or in byte mode. The MAX31782 provides three pointers that can be used for indirect

accessing of data memory. The MAX31782 has two data pointers (@DPn) and one frame pointer (@BP[OFFS]). These

pointers are implemented as registers that can be directly accessed by user software. A data memory access requires

only one system clock period.

2.4.3.1 Data Pointers

To access data memory, the data pointers are used as one of the operands in a MOVE instruction. If the data pointer is

used as a source, the core performs a load operation that reads data from the memory location addressed by the data

pointer. If the data pointer is used as destination, the core performs a store operation that writes data to the memory

location addressed by the data pointer. Following are some examples of setting and using a data pointer.

 moveDP[0],#0100h ;setpointerDP[0]toaddress100h

 moveAcc,@DP[0]  ;readdatafromlocation100h

 move@DP[0],Acc  ;writetolocation100h

The address pointed to by the data pointers can be automatically incremented or decremented. If the data pointer is

used as a source, the pointer can be incremented or decremented after the data access. If the data pointer is used as

a destination, the increment or decrement can occur prior to the data access. Following are examples of using the data

pointers increment/decrement features.

 moveAcc,@DP[0]++ ;incrementDP[0]afterread

 moveAcc,@DP[1]-- ;decrementDP[1]afterread

 move@++DP[0],Acc ;incrementDP[0]beforewrite

 move@--DP[1],Acc ;decrementDP[0]beforewrite

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 222 223

Sin comentarios

Maxim-integrated MAX31782 Manual de usuario Pagina 10