SX Users Manual Rev. 3.1
© 2000 Scenix Semiconductor, Inc. All rights reserved.
Chapter 3 Instruction Set
Load Bank Number into FSR(6:4)
FSR(6:4) = addr8(6:4)
0000 0001 1nnn
This instruction loads bits 4, 5, and 6 of the File Select Register (FSR). The high-
order bits of FSR specify the data memory bank number for subsequent memory ac-
cess instructions. You can specify any 3-bit value from 0 to 7.
In the syntax of the assembly language, you specify the bank using a full 8-bit data
memory address. The assembler encodes the three high-order bits of this address
into the instruction opcode and ignores the five low-order bits.
For the SX18/20/28AC, the bits 4:0 of FSR are left unchanged.
For the SX48/52BD, bit 7 and bits 3:0 of FSR are left unchanged. To switch
between upper and lower bank blocks, you need to set bit 7 of FSR by using the
instruction setb $04.7 or clear bit 7 by using the instruction clrb $04.7 after the
If a skip instruction is immediately followed by BANK instruction (and tested
condition is true) then two instructions are skipped and the operation consumes
three cycles. This is useful for conditional branching to another page where a PAGE
instruction precedes a JMP. If several BANK instructions immediately follow a
skip instruction then they are skipped plus the next instruction and a cycle is
consumed for each. Special attention required when switching between upper and
lower bank blocks.
SX18/20/28AC and SX18/20/28AC75:
;select highest bank
This example writes the three high-order bits of FSR with 111 and selects Bank 7,
the highest bank.