 |
전자부품 데이터시트 검색엔진 |
|
|
전자부품 데이터시트 검색엔진 |
|
DSPIC30F6015T-30E/PT 데이터시트(PDF) 21 Page - Microchip Technology |
|
|
|||||||||||||||||||||||||||||
DSPIC30F6015T-30E/PT 데이터시트(HTML) 21 Page - Microchip Technology |
|
|
21 / 236 page  © 2007 Microchip Technology Inc. DS70150C-page 19 dsPIC30F6010A/6015 The SA and SB bits are modified each time data passes through the adder/subtractor, but can only be cleared by the user. When set, they indicate that the accumulator has overflowed its maximum range (bit 31 for 32-bit saturation, or bit 39 for 40-bit saturation) and will be saturated if saturation is enabled. When saturation is not enabled, SA and SB default to bit 39 overflow and thus indicate that a catastrophic overflow has occurred. If the COVTE bit in the INTCON1 register is set, SA and SB bits will generate an arithmetic warning trap when saturation is disabled. The Overflow and Saturation Status bits can optionally be viewed in the STATUS register (SR) as the logical OR of OA and OB (in bit OAB) and the logical OR of SA and SB (in bit SAB). This allows programmers to check one bit in the STATUS register to determine if either accumulator has overflowed, or one bit to determine if either accumulator has saturated. This would be useful for complex number arithmetic which typically uses both the accumulators. The device supports three Saturation and Overflow modes. 1. Bit 39 Overflow and Saturation: When bit 39 overflow and saturation occurs, the saturation logic loads the maximally positive 9.31 (0x7FFFFFFFFF) or maximally negative 9.31 value (0x8000000000) into the target accumula- tor. The SA or SB bit is set and remains set until cleared by the user. This is referred to as ‘super saturation’ and provides protection against erro- neous data or unexpected algorithm problems (e.g., gain calculations). 2. Bit 31 Overflow and Saturation: When bit 31 overflow and saturation occurs, the saturation logic then loads the maximally posi- tive 1.31 value (0x007FFFFFFF) or maximally negative 1.31 value (0x0080000000) into the target accumulator. The SA or SB bit is set and remains set until cleared by the user. When this Saturation mode is in effect, the guard bits are not used so the OA, OB or OAB bits are never set. 3. Bit 39 Catastrophic Overflow The bit 39 Overflow Status bit from the adder is used to set the SA or SB bit, which remain set until cleared by the user. No saturation operation is performed and the accumulator is allowed to overflow (destroying its sign). If the COVTE bit in the INTCON1 register is set, a catastrophic overflow can initiate a trap exception. 2.4.2.2 Accumulator ‘Write-Back’ The MAC class of instructions (with the exception of MPY, MPY.N, ED and EDAC) can optionally write a rounded version of the high word (bits 31 through 16) of the accumulator that is not targeted by the instruction into data space memory. The write is performed across the X bus into combined X and Y address space. The following addressing modes are supported: 1. W13, Register Direct: The rounded contents of the non-target accumulator are written into W13 as a 1.15 fraction. 2. [W13]+ = 2, Register Indirect with Post-Increment: The rounded contents of the non-target accumu- lator are written into the address pointed to by W13 as a 1.15 fraction. W13 is then incremented by 2 (for a word write). 2.4.2.3 Round Logic The round logic is a combinational block, which per- forms a conventional (biased) or convergent (unbiased) round function during an accumulator write (store). The Round mode is determined by the state of the RND bit in the CORCON register. It generates a 16-bit, 1.15 data value which is passed to the data space write saturation logic. If rounding is not indicated by the instruction, a truncated 1.15 data value is stored and the least significant word is simply discarded. Conventional rounding takes bit 15 of the accumulator, zero-extends it and adds it to the ACCxH word (bits 16 through 31 of the accumulator). If the ACCxL word (bits 0 through 15 of the accumulator) is between 0x8000 and 0xFFFF (0x8000 included), ACCxH is incre- mented. If ACCxL is between 0x0000 and 0x7FFF, ACCxH is left unchanged. A consequence of this algo- rithm is that over a succession of random rounding operations, the value will tend to be biased slightly positive. Convergent (or unbiased) rounding operates in the same manner as conventional rounding, except when ACCxL equals 0x8000. If this is the case, the LSb (bit 16 of the accumulator) of ACCxH is examined. If it is ‘1’, ACCxH is incremented. If it is ‘0’, ACCxH is not modified. Assuming that bit 16 is effectively random in nature, this scheme will remove any rounding bias that may accumulate. The SAC and SAC.R instructions store either a trun- cated (SAC) or rounded (SAC.R) version of the contents of the target accumulator to data memory, via the X bus (subject to data saturation, see Section 2.4.2.4 “Data Space Write Saturation”). Note that for the MAC class of instructions, the accumulator write-back operation will function in the same manner, addressing combined MCU (X and Y) data space though the X bus. For this class of instructions, the data is always subject to rounding. |
유사한 부품 번호 - DSPIC30F6015T-30E/PT |
|
유사한 설명 - DSPIC30F6015T-30E/PT |
|
|
링크 URL |
| 개인정보취급방침 |
| ALLDATASHEET.CO.KR |
| ALLDATASHEET 가 귀하에 도움이 되셨나요? [ DONATE ] |
Alldatasheet는? | 광고문의 | 운영자에게 연락하기 | 개인정보취급방침 | 링크교환 | 제조사별 검색 All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
Korean ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
