DSPIC30F4013AT-20E/ML-ES View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

DSPIC30F4013AT-20E/ML-ES

High-Performance, 16-Bit Digital Signal Controllers

Microchip Technology 

dsPIC30F3014/4013

4.2.1 START AND END ADDRESS

The Modulo Addressing scheme requires that a start-

ing and an ending address be specified and loaded

into the 16-bit Modulo Buffer Address registers:

XMODSRT, XMODEND, YMODSRT and YMODEND

(see Table 3-3).

Note:

Y space Modulo Addressing EA calcula-

tions assume word-sized data (LSb of

every EA is always clear).

The length of a circular buffer is not directly specified. It

is determined by the difference between the

corresponding start and end addresses. The maximum

possible length of the circular buffer is 32K words

(64 Kbytes).

4.2.2

W ADDRESS REGISTER

SELECTION

The Modulo and Bit-Reversed Addressing Control reg-

ister MODCON<15:0> contains enable flags as well as

a W register field to specify the W address registers.

The XWM and YWM fields select which registers oper-

ate with Modulo Addressing. If XWM = 15, X RAGU

and X WAGU Modulo Addressing is disabled. Similarly,

if YWM = 15, Y AGU Modulo Addressing is disabled.

The X Address Space Pointer W register (XWM), to

which Modulo Addressing is to be applied, is stored in

MODCON<3:0> (see Table 3-3). Modulo Addressing is

enabled for X data space when XWM is set to any value

other than ‘15’ and the XMODEN bit is set at

MODCON<15>.

The Y Address Space Pointer W register (YWM), to

which Modulo Addressing is to be applied, is stored in

MODCON<7:4>. Modulo Addressing is enabled for Y

data space when YWM is set to any value other than

‘15’ and the YMODEN bit is set at MODCON<14>.

FIGURE 4-1:

MODULO ADDRESSING OPERATION EXAMPLE

Byte

Address

0x0800

MOV #0x800,W0

MOV W0,XMODSRT ;set modulo start address

MOV #0x863,W0

MOV W0,MODEND ;set modulo end address

MOV #0x8001,W0

MOV W0,MODCON ;enable W1, X AGU for modulo

MOV #0x0000,W0 ;W0 holds buffer fill value

MOV #0x800,W1 ;point W1 to buffer

0x0863

DO

AGAIN,#0x31 ;fill the 50 buffer locations

MOV W0,[W1++] ;fill the next location

AGAIN: INC W0,W0 ;increment the fill value

Start Addr = 0x0800

End Addr = 0x0863

Length = 0x0032 words

© 2007 Microchip Technology Inc.

DS70138E-page 37

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