HT85F2270 datasheet(104/226 Pages) HOLTEK

104 / 226 page

Rev. 1.00

104 of ��6

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

I2CCON Register

SFR Address: D8h

Bit

Name

—

ENS1

STA

STO

—

R/W

—

R/W

—

POR

—

Bit 7

Unimplemented, read as "0"

Bit 6

ENS1: I2C Enable Control

Described elsewhere

Bit 5

STA: I2C Start flag

Described elsewhere

Bit 4

STO: I2C Stop flag

Described elsewhere

Bit 3

SI: I2C Interrupt Request flag

0: No request

1: Interrupt request

The SI bit is set by hardware when one of the 25 possible I2C states takes place. This bit

must be cleared using the application program.

Bit 2

AA: I2C Acknowledge Indication flag

Described elsewhere

Bit 1~0

Unimplemented, read as "0"

Interrupt Operation

A Timer Counter overflow, an active edge or level on the external interrupt pin, a comparator

output changes state or A/D conversion completion etc, will all generate an interrupt request by

setting their corresponding request flag. When this happens, if the interrupt enable bit is set, then

the Program Counter, which stores the address of the next instruction to be executed, will be

transferred onto the stack. The Program Counter will then be loaded with a new address which

will be the value of the corresponding interrupt vector. The microcontroller will begin then fetch

its next instruction from this interrupt vector. The instruction at this vector will jump to another

section of program which is known as the interrupt service routine. Here is located the code to

control the appropriate interrupt. The interrupt service routine must be terminated with a RETI

instruction, which retrieves the original Program Counter address from the stack and allows the

microcontroller to continue with normal execution at the point where the interrupt occurred.

The various interrupt enable bits, together with their associated request flags, are shown in the

following diagram with their order of priority. The interrupts are assigned into groups. Interrupts

with higher priority can stop lower priority ones. All interrupts are categorised into 19 groups and

4 priority levels, setup using the IP0 and IP1 registers.

HT85F2270 Datasheet(PDF) 104 Page - Holtek Semiconductor Inc

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