DSPIC33FJ128MC706-I Datasheet, PDF (135/340 Pages) Microchip Technology – 16-Bit Digital Signal Controllers

dsPIC33FJXXXMCX06/X08/X10
8.0 DIRECT MEMORY ACCESS
(DMA)
Note:
This data sheet summarizes the features
of the dsPIC33FJXXXMCX06/X08/X10
family of devices. However, it is not
intended to be a comprehensive reference
source. To complement the information in
this data sheet, refer to Section 22.
“Direct Memory Access (DMA)”
(DS70182) in the “dsPIC33F Family
Reference Manual”, which is available
from the Microchip web site
(www.microchip.com).
Direct Memory Access (DMA) is a very efficient
mechanism of copying data between peripheral SFRs
(e.g., the UART Receive register and Input Capture 1
buffer) and buffers or variables stored in RAM, with
minimal CPU intervention. The DMA controller can
automatically copy entire blocks of data without
requiring the user software to read or write the
peripheral Special Function Registers (SFRs) every
time a peripheral interrupt occurs. The DMA controller
uses a dedicated bus for data transfers and, therefore,
does not steal cycles from the code execution flow of
the CPU. To exploit the DMA capability, the
corresponding user buffers or variables must be
located in DMA RAM.
The dsPIC33FJXXXMCX06/X08/X10 peripherals that
can utilize DMA are listed in Table 8-1 along with their
associated Interrupt Request (IRQ) numbers.
TABLE 8-1: PERIPHERALS WITH DMA
SUPPORT
Peripheral
IRQ Number
INT0
0
Input Capture 1
1
Input Capture 2
5
Output Compare 1
2
Output Compare 2
6
Timer2
7
Timer3
8
SPI1
10
SPI2
33
UART1 Reception
11
UART1 Transmission
12
UART2 Reception
30
UART2 Transmission
31
ADC1
13
ADC2
21
ECAN1 Reception
34
ECAN1 Transmission
70
ECAN2 Reception
55
ECAN2 Transmission
71
The DMA controller features eight identical data
transfer channels. Each channel has its own set of
control and status registers. Each DMA channel can be
configured to copy data either from buffers stored in
dual port DMA RAM to peripheral SFRs or from
peripheral SFRs to buffers in DMA RAM.
The DMA controller supports the following features:
• Word or byte sized data transfers.
• Transfers from peripheral to DMA RAM or DMA
RAM to peripheral.
• Indirect Addressing of DMA RAM locations with or
without automatic post-increment.
• Peripheral Indirect Addressing – In some
peripherals, the DMA RAM read/write addresses
may be partially derived from the peripheral.
• One-Shot Block Transfers – Terminating DMA
transfer after one block transfer.
• Continuous Block Transfers – Reloading DMA
RAM buffer start address after every block
transfer is complete.
• Ping-Pong Mode – Switching between two DMA
RAM start addresses between successive block
transfers, thereby filling two buffers alternately.
• Automatic or manual initiation of block transfers.
• Each channel can select from 20 possible
sources of data sources or destinations.
For each DMA channel, a DMA interrupt request is
generated when a block transfer is complete.
Alternatively, an interrupt can be generated when half of
the block has been filled.
© 2009 Microchip Technology Inc.
DS70287C-page 133