isppac-powr1220at8 Lattice Semiconductor Corp., isppac-powr1220at8 Datasheet - Page 32

• Manufacturer Part Number: isppac-powr1220at8
• Description: In-system Programmable Power Supply Monitoring, Sequencing And Margining Controller
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Table 1-8. I
The ispPAC-POWR1220AT8’s I
data write transaction (Figure 1-22) consists of the following operations:
To start the transaction, the master device holds the SCL line high while pulling SDA low. Address and data bits are
then transferred on each successive SCL pulse, in three consecutive byte frames of 9 SCL pulses. Address and
data are transferred on the first 8 SCL clocks in each frame, while an acknowledge signal is asserted by the slave
device on the 9th clock in each frame. Both data and addresses are transferred in a most-significant-bit-first format.
The first frame contains the 7-bit device address, with bit 8 held low to indicate a write operation. The second frame
contains the register address to which data will be written, and the final frame contains the actual data to be writ-
ten. Note that the SDA signal is only allowed to change when the SCL is low, as raising SDA when SCL is high sig-
nals the end of the transaction.
Figure 1-22. I
Reading a data byte from the ispPAC-POWR1220AT8 requires two separate bus transactions (Figure 1-23). The
first transaction writes the register address from which a data byte is to be read. Note that since no data is being
written to the device, the transaction is concluded after the second byte frame. The second transaction performs
the actual read. The first frame contains the 7-bit device address with the R/W bit held High. In the second frame
the ispPAC-POWR1220AT8 asserts data out on the bus in response to the SCL signal. Note that the acknowledge
signal in the second frame is asserted by the master device and not the ispPAC-POWR1220AT8.
1. Start the bus transaction
2. Transmit the device address (7 bits) along with a low write bit
3. Transmit the address of the register to be written to (8 bits)
4. Transmit the data to be written (8 bits)
5. Stop the bus transaction
SDA
SCL
2
C/SMBus Reserved Slave Device Addresses
START
0000 000
0000 000
0000 001
0000 010
0000 011
0000 1xx
0001 000
0001 100
0101 000
0110 111
1100 001
1111 0xx
1111 1xx
Address
2
C Write Operation
A6
1
A5
2
A4
DEVICE ADDRESS (7 BITS)
3
A3
4
R/W bit
A2
5
0
1
x
x
x
x
x
x
x
x
x
x
x
2
C/SMBus interface allows data to be both written to and read from the device. A
A1
6
A0
7
R/W
8
General Call Address
Start Byte
CBUS Address
Reserved
Reserved
HS-mode master code
NA
NA
NA
NA
NA
10-bit addressing
Reserved
ACK
I
9
2
C function Description
R7
1
R6
2
REGISTER ADDRESS (8 BITS)
R5
3
1-32
R4
4
R3
5
R2
6
R1
7
R0
8
General Call Address
Start Byte
CBUS Address
Reserved
Reserved
HS-mode master code
SMBus Host
SMBus Alert Response Address
Reserved for ACCESS.bus
Reserved for ACCESS.bus
SMBus Device Default Address
10-bit addressing
Reserved
ispPAC-POWR1220AT8 Data Sheet
ACK
9
D7
1
SMBus Function
D6
2
D5
3
WRITE DATA (8 BITS)
D4
4
D3
5
Note: Shaded Bits Asserted by Slave
D2
6
D1
7
D0
8
ACK
9
STOP