DSPIC33FJ64GP710A datasheet(70/362 Pages) MICROCHIP

70 / 362 page

dsPIC33FJXXXGPX06A/X08A/X10A

DS70593D-page 70

 2009-2012 Microchip Technology Inc.

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).

4.4.2

W ADDRESS REGISTER

SELECTION

The Modulo and Bit-Reversed Addressing Control

as a W register field to specify the W Address registers.

The XWM and YWM fields select which registers will

operate 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 4-1). 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 4-7:

MODULO ADDRESSING OPERATION EXAMPLE

0x1100

0x1163

Start Addr = 0x1100

End Addr = 0x1163

Length = 0x0032 words

Byte

Address

MOV

#0x1100, W0

MOV

W0, XMODSRT

;set modulo start address

MOV

#0x1163, 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

#0x1110, W1

;point W1 to buffer

AGAIN, #0x31

;fill the 50 buffer locations

MOV

W0, [W1++]

;fill the next location

AGAIN:

INC

W0, W0

;increment the fill value

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