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Transcript
First, the results of each TBL are rounded with the TBLS round-to-nearest-even algorithm. The following values would be returned by TBLS: TBL # 1 TBL # 2 TBL # 3 0010 0000 . 0011 1111 . 0000 0001 . Summing, the following result is obtained: 0010 0011 0000 0110 0000 . 1111 . 0001 . 0000 . Now, using the same TBL results, the sum is first calculated and then rounded according to the same algorithm: 0010 0011 0000 0110 0000 . 0111 1111 . 0111 0001 . 0111 0001 . 0101 0000 0000 0000 0000 Rounding yields: 0110 0001 . The second result is preferred. The following code sequence illustrates how addition of a series of table interpolations can be performed without loss of precision in the intermediate results: L0: TBLSN.B TBLSN.B TBLSN.B ADD.L ADD.L ASR.L BCC.B ADDQ.B L1: . . . MOTOROLA 〈ea〉, Dx 〈ea〉, Dx 〈ea〉, Dl Dx, Dm Dm, Dl #8, Dl L1 #1, Dl Long addition avoids problems with carry Move radix point Fraction MSB in carry MC68340 USER’S MANUAL 5-35
