C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 234

• Manufacturer Part Number: C8051F709-GQR
• Description: 8-bit Microcontrollers - MCU 8kB 32B EEPROM Cap Sense
• Manufacturer: Silicon Labs

Specifications of C8051F709-GQR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

C8051F70x/71x
30.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be
a receiver during the address byte, and a receiver during all data bytes. When slave events are enabled
(INH = 0), the interface enters Slave Receiver Mode when a START followed by a slave address and direc-
tion bit (WRITE in this case) is received. If hardware ACK generation is disabled, upon entering Slave
Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the
received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK
generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set
up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the
next START is detected. If the received slave address is acknowledged, zero or more data bytes are
received.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each
received byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK,
and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be
set up by the software prior to receiving the byte when hardware ACK generation is enabled.
The interface exits Slave Receiver Mode after receiving a STOP. The interface will switch to Slave Trans-
mitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 30.7 shows a typical slave write
sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that
the ‘data byte transferred’ interrupts occur at different places in the sequence, depending on whether hard-
ware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation dis-
abled, and after the ACK when hardware ACK generation is enabled.
234
S
Received by SMBus
Interface
Transmitted by
SMBus Interface
SLA
Figure 30.7. Typical Slave Write Sequence
W
A
Interrupts with Hardware ACK Disabled (EHACK = 0)
Interrupts with Hardware ACK Enabled (EHACK = 1)
Data Byte
Rev. 1.0
A
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Data Byte
A
P