1FEE 60 RTRN RTS RETURN
END
***************************************************************************
Dr. Dobb's Journal, November/December 1976, page 57.
ERRATA FOR RANKIN'S 6502
FLOATING POINT ROUTINES
Sept. 22, 1976
Dear Jim,
Subsequent to the publication of "Floating Point
Routines for the 6502" (Vol.1, No.7) an error which I made in
the LOG routine came to light which causes improper results
if the argument is less than 1. The following changes will
correct the error.
1. After: CONT JSR SWAP (1D07)
Add: A2 00 LDX =0 LOAD X FOR HIGH BYTE OF EXPONENT
2. After: STA M1+1 (1D12)
Delete: LDA =0
STA M1
Add: 10 01 BPL *+3 IS EXPONENT NEGATIVE
CA DEX YES, SET X TO $FF
86 09 STX M1 SET UPPER BYTE OF EXPONENT
3. Changes 1 and 2 shift the code by 3 bytes so add 3 to the
addresses of the constants LN10 through MHLF whenever
they are referenced. For example the address of LN10 changes
from 1DCD to 1DD0. Note also that the entry point for
LOG10 becomes 1DBF. The routines stays within the page
and hence the following routines (EXP etc.) are not affected.
Yours truly,
Roy Rankin
Dep. of Mech. Eng.
Stanford University