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HT56R22 Datasheet(PDF) 74 Page - Holtek Semiconductor Inc |
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HT56R22 Datasheet(HTML) 74 Page - Holtek Semiconductor Inc |
74 / 127 page HT56R22/HT56R23/HT56R24/HT56R25/HT56R26 Rev. 1.30 74 December 26, 2014 ¨ RXAK The RXAK flag is the receive acknowledge flag. When the RXAK bit has been reset to zero it means that a correct acknowledge signal has been re- ceived at the 9th clock, after 8 bits of data have been transmitted. When in the transmit mode, the transmitter checks the RXAK bit to determine if the receiver wishes to receive the next byte. The trans- mitter will therefore continue sending out data until the RXAK bit is set high. When this occurs, the transmitter will release the SDA line to allow the master to send a STOP signal to release the bus. ¨ SRW The SRW bit is the Slave Read/Write bit. This bit de- termines whether the master device wishes to transmit or receive data from the I 2C bus. When the transmitted address and slave address match, that is when the HAAS bit is set high, the device will check the SRW bit to determine whether it should be in transmit mode or receive mode. If the SRW bit is high, the master is requesting to read data from the bus, so the device should be in transmit mode. When the SRW bit is zero, the master will write data to the bus, therefore the device should be in receive mode to read this data. ¨ TXAK The TXAK flag is the transmit acknowledge flag. Af- ter the receipt of 8-bits of data, this bit will be trans- mitted to the bus on the 9th clock. To continue receiving more data, this bit has to be reset to zero before further data is received. ¨ HTX The HTX flag is the transmit/receive mode bit. This flag should be set high to set the transmit mode and low for the receive mode. ¨ HBB The HBB flag is the I 2C busy flag. This flag will be high when the I 2C bus is busy which will occur when a START signal is detected. The flag will be reset to zero when the bus is free which will occur when a STOP signal is detected. ¨ HASS The HASS flag is the address match flag. This flag is used to determine if the slave device address is the same as the master transmit address. If the ad- dresses match then this bit will be high, if there is no match then the flag will be low. ¨ HCF The HCF flag is the data transfer flag. This flag will be zero when data is being transferred. Upon com- pletion of an 8-bit data transfer the flag will go high and an interrupt will be generated. I 2C Control Register - SIMAR The SIMARregister is also used by the SPI interface but has the name SIMCTL2. The SIMAR register is the location where the 7-bit slave address of the microcontroller is stored. Bits 1~7 of the SIMAR register define the microcontroller slave ad- dress. Bit 0 is not defined. When a master device, which is connected to the I 2C bus, sends out an address, which matches the slave address in the SIMARregister, the microcontroller slave device will be selected. Note that the SIMAR register is the same register as SIMCTL2 which is used by the SPI interface. I 2C Bus Communication Communication on the I 2C bus requires four separate steps, a START signal, a slave device address trans- mission, a data transmission and finally a STOP signal. When a START signal is placed on the I 2C bus, all de- vices 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 HAAS bit in the SIMCTL1 register will be set and an I 2C interrupt will be generated. After entering the interrupt service rou- tine, the microcontroller slave device must first check the condition of the HAAS 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 SRW bit. This bit will be checked by the microcontroller to de- termine whether to go into transmit or receive mode. Be- fore 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 SIMAR. Step 2 Set the SIMEN bit in the SIMCTL0 register to ²1² to en- able the I 2C bus. Step 3 Set the ESIM bit of the interrupt control register to en- able the I 2C bus interrupt. S I M A R R e g i s t e r b 7 N o t i m p l e m e n t e d , r e a d a s " 0 " I 2 C d e v i c e s l a v e a d d r e s s b 0 S A 5 S A 4 S A 6 S A 0 S A 3 S A 2 S A 1 I 2C Slave Address Register - SIMAR |
Similar Part No. - HT56R22_14 |
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Similar Description - HT56R22_14 |
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