Z8FMC16100 Series Flash MCU
Product Specification
179
S
Slave Address
W=0
A
Data
A
Data
A
Data
A/A
P/S
Figure 32. Data Transfer Format—Slave Receive Transaction with 7-Bit Address
1. The software configures the controller for operation as a slave in 7-bit addressing
mode, as follows.
a. Initialize the MODEfield in the I2C Mode Register for either SLAVE ONLY mode
or MASTER/SLAVE mode with 7-bit addressing.
b. Optionally set the GCEbit.
c. Initialize the SLA[6:0]bits in the I2C Slave Address Register.
d. Set IEN= 1 in the I2C Control Register. Set NAK= 0 in the I2C Control Register.
2. The bus master initiates a transfer, sending the address byte. In SLAVE mode, the I2C
controller recognizes its own address and detects that the R/W bit = 0 (written from
the master to the slave). The I2C controller acknowledges, indicating it is available to
accept the transaction. The SAMbit in the I2CISTAT Register is set to 1, causing an
interrupt. The RDbit in the I2CISTAT Register is cleared to 0, indicating a Write to the
slave. The I2C controller holds the SCL signal Low, waiting for the software to load
the first data byte.
3. The software responds to the interrupt by reading the I2CISTAT Register (which
clears the SAMbit). After seeing the SAMbit to 1, the software checks the RDbit.
Because RD= 0, no immediate action is required until the first byte of data is received.
If software is only able to accept a single byte it sets the NAKbit in the I2CCTL Regis-
ter at this time.
4. The master detects the Acknowledge and sends the byte of data.
5. The I2C controller receives the data byte and responds with Acknowledge or Not
Acknowledge depending on the state of the NAKbit in the I2CCTL Register. The I2C
controller generates the receive data interrupt by setting the RDRFbit in the I2CISTAT
Register.
6. The software responds by reading the I2CISTAT Register, finding the RDRFbit = 1
and reading the I2CDATA Register clearing the RDRFbit. If software can accept only
one more data byte it sets the NAKbit in the I2CCTL Register.
7. The master and slave loops through steps 4 to 6 until the master detects a Not
Acknowledge instruction or runs out of data to send.
8. The master sends the STOPor RESTARTsignal on the bus. Either of these signals can
cause the I2C controller to assert a STOP interrupt (the STOPbit = 1 in the I2CISTAT
Register). Because the slave received data from the master, the software takes no
action in response to the STOP interrupt other than reading the I2CISTAT Register to
clear the STOPbit in the I2CISTAT Register.
PS024604-1005
P R E L I M I N A R Y
Slave Transactions
ZILOG [ ZILOG, INC. ]
