HT56RB688_13 datasheet(82/164 Pages) HOLTEK

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2C Bus Communication

Communication on the I

2C bus requires four separate steps, a START signal, a slave device address

transmission, a data transmission and finally a STOP signal. When a START signal is placed on the I

bus, all devices on the bus will receive this signal and be notified of the imminent arrival of data on the

bus. The first seven bits of the data will be the slave address with the first bit being the MSB. If the

address of the microcontroller matches that of the transmitted address, the HAASn bit in the

SIMnCTL1 register will be set and an I

2C interrupt will be generated. After entering the interrupt

service routine, the microcontroller slave device must first check the condition of the HAASn bit to

determine whether the interrupt source originates from an address match or from the completion of an

8-bit data transfer. During a data transfer, note that after the 7-bit slave address has been transmitted,

the following bit, which is the 8th bit, is the read/write bit whose value will be placed in the SRWn bit.

This bit will be checked by the microcontroller to determine whether to go into transmit or receive

mode. Before any transfer of data to or from the I

2C bus, the microcontroller must initialise the bus.

The following are steps to achieve this:

Step 1

Write the slave address of the microcontroller to the I

2C bus address register SIMnAR.

Step 2

Set the SIMnEN bit in the SIMnCTL0 register to ²1² to enable the I

2C bus.

Step 3

Set the ESIMn bit of the interrupt control register to enable the I

2C bus interrupt.

Rev. 1.10

April 15, 2013

HT56RB688

TinyPowerTM A/D type Smart Card OTP MCU

with LCD, DAC, ISO 7816 and USB Interfaces

S t a r t

W r i t e S l a v e

A d d r e s s t o S I M n A R

S E T S n S I M [ 2 : 0 ] = 1 1 0

S E T S I M n E N

I 2 C B u s

I n t e r r u p t = ?

E n a b l e

D i s a b l e

S E T E S I M n

W a i t f o r I n t e r r u p t

G o t o M a i n P r o g r a m

C L R E S I M n

P o l l S I M F n t o d e c i d e

w h e n t o g o t o I 2 C B u s I S R

G o t o M a i n P r o g r a m

2C Bus Initialisation Flow Chart

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