CP3UB26 datasheet(7/268 Pages) NSC

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3.21

DMA CONTROLLER

The Direct Memory Access Controller (DMAC) can speed

up data transfer between memory and I/O devices or be-

tween two memories, relative to data transfers performed di-

rectly by the CPU. A method called cycle-stealing allows the

CPU and the DMAC to share the CPU bus efficiently. The

DMAC implements four independent DMA channels. DMA

requests from a primary and a secondary source are recog-

nized for each DMA channel, as well as a software DMA re-

quest issued directly by the CPU. Table 1 shows the DMA

channel assignment on the CP3UB26 architecture. The fol-

lowing on-chip modules can assert a DMA request to the

DMAC:

•

CR16C (Software DMA request)

•USB

•

USART

•

Advanced Audio Interface

•

CVSD/PCM Converter

Table 1 shows how the four DMA channels are assigned

to the modules listed above.

Table 1

DMA Channel Assignment

The interface can handle data words of either 8- or 16-bit

length and data frames can consist of up to four slots.

In the normal mode of operation, the interface only transfers

one word at a periodic rate. In the network mode, the inter-

face transfers multiple words at a periodic rate. The periodic

rate is also called a data frame and each word within one

frame is called a slot. The beginning of each new data frame

is marked by the frame sync signal.

3.22

SERIAL DEBUG INTERFACE

The Serial Debug Interface module (SDI module) provides

a JTAG-based serial link to an external debugger, for exam-

ple running on a PC. In addition, the SDI module integrates

an on-chip debug module, which allows the user to set up to

eight hardware breakpoints on instruction execution and

data transfer. The SDI module can act as a CPU bus master

to access all memory mapped resources, such as RAM and

peripherals. Therefore it also allows for fast program code

download into the on-chip Flash program memory using the

JTAG interface.

3.23

DEVELOPMENT SUPPORT

In addition to providing the features needed for the next gen-

eration of embedded products, the CP3UB26 devices are

backed up by the software resources designers need for

rapid product development, including an operating system,

peripheral drivers, reference designs, and an integrated de-

velopment environment.

National Semiconductor offers a complete and industry-

proven application development environment for CP3UB26

applications, including the IAR Embedded Workbench,

iSYSTEM winIDEA and iC3000 Active Emulator, Develop-

ment Board, and Application Software. See your National

Semiconductor sales representative for current information

on availability and features of emulation equipment and

evaluation boards.

Channel

Primary/

Secondary

Peripheral

Transaction

Primary

USB

Read/Write

Secondary

UART0

Read

Primary

UART0

Write

Secondary

Unused

N/A

Primary

AAI

Read

Secondary

CVSD/PCM

Read

Primary

AAI

Write

Secondary

CVSD/PCM

Write

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