section 7 - Index of
section 7 - Index of section 7 - Index of
(Rn) ± Nn MOD MWHERE Nn = 2k (Le., P = 1)Figure 4-12 Linear Addressing with a Modulo Modifierplus 20 (M-1». The Mn register is loaded with the value 20 (M-1). The offset register isarbitrarily chosen to be 15 (Nn~M). The address pointer is not required to start at the loweraddress boundary and can begin anywhere within the defined modulo address range -. i.e., within the lower boundary + (2k) address region. The address pointer, Rn, is arbitrarilychosen to be 75 in this example. When R2 is post-incremented by the offset by the MOVEinstruction, instead of pointing to 90 (as it would in the linear mode) it wraps around to 69.If the address register pointer increments past the upper boundary of the buffer (base addressplus M-1), it will wrap around to the base address. If the address decrements pastthe lower boundary (base address), it will wrap around to the base address plus M-1.If Rn is outside the valid modulo buffer range and an operation occurs that causes Rn tobe updated, the contents of Rn will be updated according to modulo arithmetic rules. Forexample, a MOVE BO,X:(RO)+ NO instruction (where RO=6, MO=5, and NO=O) would apparentlyleave RO unchanged since NO=O. However, since RO is above the upperboundary, the AGU calculates RO+ NO-MO-1 for the new contents of RO and sets RO=O.The MOVE instruction in Figure 4-13 takes the contents of the XO register and moves it toa location in the X memory pointed to by (R2), and then (R2) is updated modulo 21. The
EXAMPLE: MOVE XO,X:(R2)+NLET:M2 00 ..... 0010100 I MODULUS=21N2 00 ..... 0001111 I OFFSET=15R2 00 ..... 1001011 I POINTER=75-Figure 4-13 Modulo Modifier Examplenew value of R2 is not 90 (75+ 15), which would be the case if linear arithmetic had beenused, but rather is 69 since modulo arithmetic was used.4.4.2.2.2 Mn=$8001 to $BFFFIn this range, the modulo (M) equals (Mn+ 1 )-$8000, where Mn is the value in the modifierregister (see Table 4-2). This range firmly restricts the address register to the samebuffer, causing the address register to wrap around within the buffer. This multiple wraparoundaddressing feature reduces argument overhead and is useful for decimation,interpolation, and waveform generation.The address modification is performed modulo M, where M may be any power of 2 in therange from 21 to 214. Modulo M arithmetic causes the address register value to remainwithin an address range of size M defined by a lower and upper address boundary. Thevalue M-1 is stored in the modifier register Mn least significant 14 bits while the two mostsignificant bits are set to '10'. The lower boundary (base address) value must have zeroesin the k LSBs, where 2k = M, and therefore must be a multiple of 2k. The upper boundaryis the lower boufldary plus the modulo size minus one (base address plus M-1).For example, to create a circular buffer of 32 stages, M is chosen as 32 and the lower addressboundary must have its 5 least significant bits equal to zero (2 k = 32, thus k = 5).
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- Page 49 and 50: CASE I: IF AO < $800000 (1/2), THEN
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- Page 67 and 68: EXAMPLE: MOVE X1,X: (R2)+N2BEFORE E
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(Rn) ± Nn MOD MWHERE Nn = 2k (Le., P = 1)Figure 4-12 Linear Addressing with a Modulo Modifierplus 20 (M-1». The Mn register is loaded with the value 20 (M-1). The <strong>of</strong>fset register isarbitrarily chosen to be 15 (Nn~M). The address pointer is not required to start at the loweraddress boundary and can begin anywhere within the defined modulo address range -. i.e., within the lower boundary + (2k) address region. The address pointer, Rn, is arbitrarilychosen to be 75 in this example. When R2 is post-incremented by the <strong>of</strong>fset by the MOVEinstruction, instead <strong>of</strong> pointing to 90 (as it would in the linear mode) it wraps around to 69.If the address register pointer increments past the upper boundary <strong>of</strong> the buffer (base addressplus M-1), it will wrap around to the base address. If the address decrements pastthe lower boundary (base address), it will wrap around to the base address plus M-1.If Rn is outside the valid modulo buffer range and an operation occurs that causes Rn tobe updated, the contents <strong>of</strong> Rn will be updated according to modulo arithmetic rules. Forexample, a MOVE BO,X:(RO)+ NO instruction (where RO=6, MO=5, and NO=O) would apparentlyleave RO unchanged since NO=O. However, since RO is above the upperboundary, the AGU calculates RO+ NO-MO-1 for the new contents <strong>of</strong> RO and sets RO=O.The MOVE instruction in Figure 4-13 takes the contents <strong>of</strong> the XO register and moves it toa location in the X memory pointed to by (R2), and then (R2) is updated modulo 21. The
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