A fast 80X86 assembly language module to low-pass filter digital data

This short assembly language procedure, which can be called from a high level language program, will low-pass filter an array of digital data. This is a well known algorithm coded in assembly language for speed: it filters 512 data points in 5 ms in a 16 MHz 386 microcomputer. The procedure can handle up to 32 kb of binary data, 12-16 bits wide, from an on-line experiment or from an already stored file. The user chooses the cutoff frequency selecting a factor and how many times the data are passed through the filter. The filter has an excellent time-domain response which makes it ideal for physiological pulse recording. The listings of the source assembly routine and of a sample Pascal program that calls it are provided in the text.