C8051F310 datasheet(156/224 Pages) ETC1

156 / 224 page

C8051F310/1/2/3/4/5/6/7

156

Rev. 1.6

14.5.4. Slave Transmitter Mode

Serial data is transmitted on SDA and the clock is received on SCL. When slave events are enabled (INH

= 0), the interface enters Slave Receiver Mode (to receive the slave address) when a START followed by a

slave address and direction bit (READ in this case) is received. Upon entering Slave Transmitter Mode, an

interrupt is generated and the ACKRQ bit is set. Software responds to the received slave address with an

ACK, or ignores the received slave address with a NACK. If the received slave address is ignored, slave

interrupts will be inhibited until a START is detected. If the received slave address is acknowledged, data

should be written to SMB0DAT to be transmitted. The interface enters Slave Transmitter Mode, and trans-

mits one or more bytes of data. After each byte is transmitted, the master sends an acknowledge bit; if the

acknowledge bit is an ACK, SMB0DAT should be written with the next data byte. If the acknowledge bit is

a NACK, SMB0DAT should not be written to before SI is cleared (Note: an error condition may be gener-

ated if SMB0DAT is written following a received NACK while in Slave Transmitter Mode). The interface

exits Slave Transmitter Mode after receiving a STOP. Note that the interface will switch to Slave Receiver

Mode if SMB0DAT is not written following a Slave Transmitter interrupt. Figure 14.8 shows a typical Slave

Transmitter sequence. Two transmitted data bytes are shown, though any number of bytes may be trans-

mitted. Notice that the ‘data byte transferred’ interrupts occur after the ACK cycle in this mode.

Figure 14.8. Typical Slave Transmitter Sequence

SLA

Data Byte

S = START

P = STOP

N = NACK

R = READ

SLA = Slave Address

Received by SMBus

Interface

Transmitted by

SMBus Interface

Interrupt

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