PIC24H datasheet(29/290 Pages) MICROCHIP

29 / 290 page

Preliminary

DS70175D-page 29

PIC24H

FIGURE 3-4:

DATA MEMORY MAP FOR PIC24H DEVICES WITH 16 KBYTES RAM

3.2.5

DMA RAM

Every PIC24H device contains 2 Kbytes of dual ported

DMA RAM located at the end of data space. Memory

locations in the DMA RAM space are accessible

simultaneously by the CPU and the DMA controller

module. DMA RAM is utilized by the DMA controller to

store data to be transferred to various peripherals using

DMA, as well as data transferred from various

peripherals using DMA. The DMA RAM can be

accessed by the DMA controller without having to steal

cycles from the CPU.

When the CPU and the DMA controller attempt to

concurrently write to the same DMA RAM location, the

hardware ensures that the CPU is given precedence in

accessing the DMA RAM location. Therefore, the DMA

RAM provides a reliable means of transferring DMA

data without ever having to stall the CPU.

0x0000

0x07FE

0xFFFE

LSB

Address

16 bits

LSB

MSB

Address

0x0001

0x07FF

0xFFFF

Optionally

Mapped

into Program

Memory

0x47FF

0x47FE

0x0801

0x0800

Near

Data

2-Kbyte

SFR Space

16-Kbyte

SRAM Space

8-Kbyte

Space

0x8001

0x8000

0x4800

0x4801

0x3FFE

0x4000

0x3FFF

0x4001

0x1FFE

0x1FFF

SFR Space

X Data

Unimplemented (X)

DMA RAM

X Data RAM (X)

Note:

DMA RAM can be used for general

purpose data storage if the DMA function

is not required in an application.

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