7. I
2
C Interface > Boot Load Sequence
166
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
7.7.3
SMBus Alert Response Protocol Support
The Tsi578 supports the SMBus Alert Response Protocol as either master or slave. As a master, an
external device can be polled using a master read operation. As a slave, the Tsi578 slave interface
responds to the Alert Response Address with the Tsi578’s slave device address based on the value of
ALERT_FLAG in the
C Slave Access Status Register”
, if enabled in ALRT_EN
C Slave Configuration Register”
. Once the alert response is given and the Tsi578’s slave device
address is returned, the ALERT_FLAG is de-asserted. For the register fields indicated in
reference the master interface registers I2C_MST_CFG, I2C_MST_CNTRL, and I2C_MST_RDATA,
as well as the slave configuration register I2C_SLV_CFG.
Figure 35: SMBus Alert Response Protocol
7.8
Boot Load Sequence
Unless the I2C_DISABLE pin is held high, the Tsi578 will perform a post-hard reset register
initialization sequence where it reads data from one or more external EEPROM devices (for more
information about I2C_DISABLE, see “Power-up Options” in this document). This data initializes the
Tsi578’s internal registers. The boot load sequence occurs only after a full chip reset, and follows the
steps shown in
. The boot load sequence is controlled by the contents of the
I2C_BOOT_CNTRL register.
RD0=DevAdr
P
S
ARA
A
Rd
N
SMBus Alert Response (master interface), DEV_ADDR = 0001100, PA_SIZE=0, SIZE=1, DORDER=1, WRITE=0
S
= Start Condition
P
= Stop Condition
A
= ACK
N
= NACK
Unshaded
= Master is driving the bus
Shaded
= Slave is driving the bus
P
S
ARA
N
Rd
SMBus Alert Response (slave interface), ALRT_EN=1, ALERT_FLAG=1
SMBus Alert Response (slave interface), ALRT_EN=0 or ALERT_FLAG=0
SLV_ADDR
P
S
ARA
A
Rd
N
P
S
ARA
N
Rd
No device responds to alert poll, operation fails with MA_NACK interrupt
A device returns their address, loaded into read data register
Rd
= Read mode bit (1)
* For information about DEV_ADDR, DORDER, and PA_SIZE, see
. For more information about SIZE and WRITE, see
.
For more information about ALRT_EN, see
C Slave Configuration Register”
.
No alert asserted from Tsi578, poll is NACK’d
Alert asserted from Tsi578, slave address is returned
ARA
= SMBus Alert Response Address (0001100)
DevAdr
= Slave address of external device asserting alert
SLV_ADDR
= Slave address of Tsi578 from I2C_SLV_CFG
RD0
= LSB of I2C_MST_RDATA (data returned here)