ST7LUS5 datasheet(24/124 Pages) STMICROELECTRONICS

24 / 124 page

Central processing unit

ST7LUS5, ST7LU05, ST7LU09

24/124

Figure 6.

CPU registers

5.3.4

Condition code register (CC)

The 8-bit condition code register contains the interrupt mask and four flags representative of

the result of the instruction just executed. This register can also be handled by the PUSH

and POP instructions.

These bits can be individually tested and/or controlled by specific instructions.

ACCUMULATOR

X INDEX REGISTER

Y INDEX REGISTER

STACK POINTER

CONDITION CODE REGISTER

PROGRAM COUNTER

11 H I N Z

RESET VALUE = RESET VECTOR @ FFFEh-FFFFh

PCH

PCL

8 7

RESET VALUE = 1X

11X 1X X

RESET VALUE = XXh

X = Undefined value

RESET VALUE = STACK HIGHER ADDRESS

Reset value: 111x1xxx

765

432

111

R/W

Table 5.

CC register description

Bit Name

Function

7:5

Reserved, must remain set.

Half carry

This bit is set by hardware when a carry occurs between bits 3 and 4 of the ALU

during an ADD or ADC instruction. It is reset by hardware during the same

instructions.

0: No half carry has occurred.

1: A half carry has occurred.

This bit is tested using the JRH or JRNH instruction. The H bit is useful in BCD

arithmetic subroutines.

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