DSPIC30F6010 MICROCHIP [Microchip Technology], DSPIC30F6010 Datasheet - Page 35

• Manufacturer Part Number: DSPIC30F6010
• Description: High-Performance Digital Signal Controllers
• Manufacturer: MICROCHIP [Microchip Technology]

4.2.1
The Modulo addressing scheme requires that a
starting and an end 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 determined by the difference between the corre-
sponding start and end addresses. The maximum pos-
sible length of the circular buffer is 32K words
(64 Kbytes).
FIGURE 4-1:
 2004 Microchip Technology Inc.
Note:
Byte
Address
0x1100
0x1163
START AND END ADDRESS
Y-space modulo addressing EA calcula-
tions assume word-sized data (LS bit of
every EA is always clear).
Start Addr = 0x1100
End Addr = 0x1163
Length = 0x0032 words
MODULO ADDRESSING OPERATION EXAMPLE
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
DO
MOV
AGAIN: INC
Preliminary
#0x1100,W0
W0, XMODSRT
#0x1163,W0
W0,MODEND
#0x8001,W0
W0,MODCON
#0x0000,W0
#0x1110,W1
AGAIN,#0x31
W0, [W1++]
W0,W0
4.2.2
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 will
operate with modulo addressing. If XWM = 15, X RAGU
and X WAGU modulo addressing are disabled. Simi-
larly, 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
dsPIC30F6010
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