SX User’s Manual Rev. 3.1 84 © 2000 Scenix Semiconductor, Inc. All rights reserved. www.scenix.com Chapter 3 Instruction Set 3.6.16    IREAD Read Word from Instruction Memory Operation: MODE:W = data at (MODE:W) Bits affected: none Opcode: 0000 0100 0001 Description: This instruction allows the device to transfer data from instruction memory into
data memory. It concatenates the lower four bits of the MODE register with W to
make a 12-bit address, using the MODE register bits for the high-order part and W
for the low-order part. It reads the 12-bit word from program memory at that ad-
dress. Then it writes the four high-order bits of the word into the lower four bits of
the MODE register, and writes the eight low-order bits of the word into W. The four
high-order bits of the MODE register are cleared to zero. Figure 3-1 shows how the MODE and W register are used to specify the program memory address and to contain the 12-bit result. Figure 3-1 Program Counter Loading for Call Instruction Upper 4 bits Lower 8 bits Lower 8 bits Upper 4 bits 0 0 0 MODE
Register W
Register 12 12 Program Memory
Address Pointer Program Data Program
Memory = Hardwired to 0 for SX28AC = Programmable with MOV M, W for SX48/52BD Hardwired to 0 for all devices