DSPIC30F6010A MICROCHIP [Microchip Technology], DSPIC30F6010A Datasheet - Page 37

• Manufacturer Part Number: DSPIC30F6010A
• Description: High-Performance, 16-bit Digital Signal Controllers
• Manufacturer: MICROCHIP [Microchip Technology]

4.2.1
The Modulo Addressing scheme requires that a
starting 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).
The length of a circular buffer is not directly specified. It
is
corresponding start and end addresses. The maximum
possible length of the circular buffer is 32K words
(64 Kbytes).
FIGURE 4-1:
© 2011 Microchip Technology Inc.
Note:
Byte
Address
0x1100
0x1163
determined
START AND END ADDRESS
Y space Modulo Addressing EA calcula-
tions assume word-sized data (LSb of
every EA is always clear).
Start Addr = 0x1100
End Addr = 0x1163
Length = 0x0032 words
by
the
MODULO ADDRESSING OPERATION EXAMPLE
difference
between
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
DO
MOV
AGAIN: INC
the
#0x1100,W0
W0, XMODSRT
#0x1163,W0
W0,MODEND
#0x8001,W0
W0,MODCON
#0x0000,W0
#0x1110,W1
AGAIN,#0x31
W0, [W1++]
W0,W0
dsPIC30F6010A/6015
4.2.2
The Modulo and Bit-Reversed Addressing Control
register, 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 will operate with Modulo Addressing. If
XWM = 15, X RAGU and X WAGU Modulo Addressing
are 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>.
;set modulo start address
;set modulo end address
;enable W1, X AGU for modulo
;W0 holds buffer fill value
;point W1 to buffer
;fill the 50 buffer locations
;fill the next location
;increment the fill value
W ADDRESS REGISTER
SELECTION
DS70150E-page 37