PM0044 datasheet(59/162 Pages) STMICROELECTRONICS

59 / 162 page

PM0044

STM8 addressing modes

Doc ID 13590 Rev 3

59/162

6.14

Bit Direct (Long) Relative addressing mode

This addressing mode is a combination between the Bit Direct addressing mode (for data

addressing) and Relative Direct mode (for PC computation).

The data byte required for the operation is found by its memory address, which follows the

op-code. The bit used for the test operation is selected by the bit selector which is encoded

in the instruction op-code. Following the logical test operation, the PC register value can be

modified, by adding an 8-bit signed offset to it.

The data address is a word, thus allowing 0000 to FFFF addressing space (requires 2 bytes

after the op-code). The bit selector #n (n=0 to 7) selects the nth bit from the byte pointed to

by the address. The offset follows the op-code and data address.

Example:

Table 39.

Overview of Bit Direct (Long) Relative addressing mode

Addressing mode

Syntax

EA formula

Ptr Adr

Ptr Size

Dest adr

Bit

Long

Direct

Relative

longmem, #pos, off

(longmem)

op + 1..2

Word

0000..FFFF

PC = PC + off

op + 3

Byte

PC +127/-

128

Table 40.

Available Bit Direct Relative instructions

Instructions

Functions

BTJT, BTJF

Bit Test and Jump

104B

DRA

dc.b

$00

; Port A data

(input

value)

bit0

equ

$0 ; data bit 0

04A7

7201104BFB wait_1

BTJF

DRA, bit0, wait_1

04AC

....

cont_0

Action:

Test = select_bit(0, ($4B)) = select_bit(0, DRA)

if (Test /= 1)

then

PC = PC + $FB

= $0004AC - $05 =

$0004A7

else

PC = PC

= $0004AC

PM0044 数据表(PDF) 59 Page - STMicroelectronics

PM0044 数据表(HTML) 59 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载