The CYASM Assembler User Guide has detailed discussion on Cypress' M8 assembly language. This document comes with the Cypress Lab CD. If you have already installed the CYDB tool from the CD, you can go to the Cypress/Cydb/Doc/Cyasm folder to get the file. The assembler, CYASM.EXE, is located at Cypress/Cydb/Bin.
Please find attached the CYASM Assembler User's Guide and CYASM.EXE below.