DSPIC30F2012AT-20E/ML View Datasheet(PDF) - Microchip Technology
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Description
Manufacturer
DSPIC30F2012AT-20E/ML Datasheet PDF : 206 Pages
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dsPIC30F2011/2012/3012/3013
4.2.1 START AND END ADDRESS
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).
Note:
Y space Modulo Addressing EA
calculations 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
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 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 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
0x1100
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
0x1163
DO
AGAIN,#0x31
MOV W0,[W1++]
AGAIN: INC W0,W0
;fill the 50 buffer locations
;fill the next location
;increment the fill value
Start Addr = 0x1100
End Addr = 0x1163
Length = 0x0032 words
© 2008 Microchip Technology Inc.
DS70139F-page 45
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