PIC24HJ32GP302_11 Datasheet, PDF (28/368 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJ32GP302/304, PIC24HJ64GPX02/X04 AND PIC24HJ128GPX02/X04
4.2.5 DMA RAM
The PIC24HJ32GP302/304 devices contain 1 Kbytes
of dual ported DMA RAM located at the end of X data
space. The PIC24HJ64GPX02/X04 and
PIC24HJ128GPX02/X04 devices contain 2 Kbytes of
dual ported DMA RAM located at the end of X data
space, and is a part of X 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.
Note:
DMA RAM can be used for general
purpose data storage if the DMA function
is not required in an application.
FIGURE 4-3:
DATA MEMORY MAP FOR PIC24HJ32GP302/304 DEVICES WITH 4 KB RAM
2 Kbyte
SFR Space
MSb
Address
0x0000
0x07FF
0x0801
MSb
16 bits
LSb
SFR Space
LSb
Address
0x0000
0x07FE
0x0800
4 Kbyte
SRAM Space
0x13FF
0x1401
0x17FF
0x1801
X Data RAM (X)
DMA RAM
0x13FE
0x1400
0x17FE
0x1800
6 Kbyte
Near
Data
Space
0x8001
0x8000
Optionally
Mapped
into Program
Memory
X Data
Unimplemented (X)
0xFFFF
0xFFFE
DS70293E-page 28
© 2011 Microchip Technology Inc.