SX User’s Manual Rev. 3.1 80 © 2000 Scenix Semiconductor, Inc. All rights reserved. Chapter 3 Instruction Set 3.6.12    DEC fr Decrement fr Operation: fr = fr -1 Bits affected: Z Opcode: 0000 111f ffff Description: This instruction decrements the specified register file by one. If  the  file  register  contains  01h,  it  is  decremented  to  00h  and  the  Z  bit  is  set. Otherwise, the bit is cleared. If the file register contains 00h, it is decremented to FFh. Cycles: 1 Example: dec $18 This example decrements file register 18h.