CP80S54 Datasheet, PDF (6/47 Pages) List of Unclassifed Manufacturers – EPROM/ROM-Based 8-Bit Microcontroller Series

CP80S54/56
2.0 FUNCTIONAL DESCRIPTIONS
2.1 Operational Registers
2.1.1 INDF (Indirect Addressing Register)
Address
00h (r/w)
Name
INDF
B7
B6
B5
B4
B3
B2
B1
B0
Uses contents of FSR to address data memory (not a physical register)
The INDF Register is not a physical register. Any instruction accessing the INDF register can actually access the
register pointed by FSR Register. Reading the INDF register itself indirectly (FSR=”0”) will read 00h. Writing to the
INDF register indirectly results in a no-operation (although status bits may be affected).
The bits 5-0 of FSR register are used to select up to 64 registers (address: 00h ~ 3Fh).
EXAMPLE 2.1: INDIRECT ADDRESSING
‧ Register file 38 contains the value 10h
‧ Register file 39 contains the value 0Ah
‧ Load the value 38 into the FSR Register
‧ A read of the INDF Register will return the value of 10h
‧ Increment the value of the FSR Register by one (@FSR=39h)
‧ A read of the INDR register now will return the value of 0Ah.
FIGURE 2.1: Direct/Indirect Addressing
Direct Addressing
5 from opcode 0
Indirect Addressing
5 from FSR register 0
location select
00h
location select
addressing INDF register
3Fh
Rev0.1 Nov 30, 2005
P.6/CP80S54/S56