ST10F166 datasheet(28/62 Pages) STMICROELECTRONICS

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ST10F166

15 SOFTWARE DESCRIPTION

Addressing Modes

The ST10F166 offers different powerful addressing modes to facilitate rapid access

on word, byte and bit data, or to specify the destination address of a branch instruc-

tion. The addressing modes are subdivided in six different categories as follows.

Short addressing modes: an implicit base offset address is used to specify a phys-

ical 18-bit address.

EA = Base Address + k Short Address.

k= 1 or2

EA = Effective Address

This mode allows direct access to any GPR or SFR and any word in the bit-address-

able memory space. (in case of a byte operation on an SFR, only the low byte can be

accessed via ‘reg’).

Long addressing modes: one of the four DPP registers, selected by bit 15 and 14 of

the 16-bit address, is used to specify a physical 18-bit address.

EA = Contents of DPPi + Page Offset Address

i: specified by bit 15, 14 of the 16 bit address.

Page Offset Address: bit 13 to 0 of the 16 bit address.

In this mode, any word or byte data within the entire memory space can be accessed

directly . Word accesses may not be performed on odd byte addresses, otherwise a

hardware trap will occur.

Indirect addressing modes: a 16-bit long address is specified indirectly by the con-

tents of a word GPR which is specified directly by a short address. Any word GPR can

be used, except for arithmetic, logical and compare instructions, where only R0 to R3

are allowed. There are also certain modes which allow decrementing or incrementing

the indirect address pointers by a data-type-dependent value.

Long Address = [GPR Address] + Constant

EA = Contents of DPPi + Page Offset Address

i: specified by bit 15, 14 of the Long Address.

Page Offset Address: bit 13 to 0 of the long address

Long Address Long Address

bit15,14 specify i bit 13 to 0

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