The detail on the instructions are in: httt://www.bitsavers.org/pdf/ibm/360/funcChar/A26-5847-3_360-20_funChar_Apr67.pdf
The HRTBP360 program that IBM still distributes, I am told, with HASP, uses macros for the 360/20 specific instructions. (It was written to assembler with OS/360 or OS/VS2 assemblers.) The macros seem to still work with new assemblers. -- glen
