Data Sheet
526
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
If the operation is a read, the 10-bit address will be followed by a repeated START and reception of “11110 ADDR[9:8] 1”
and the second address interrupt will be received with the DIR bit set. The slave matches on the second address as it
remembers that is was addressed by the previous 10-bit address.
Figure 27-12.10-bit Addressing
PMBus Group Command
When the group command bit is set (CTRLB.GCMD) and 7-bit addressing is used, a STOP interrupt will be generated if
the slave has been addressed since the last STOP condition.
The group command protocol is used to send commands to more than one device. The commands are sent in one
continuous transmission with a single STOP condition at the end. When the STOP condition is detected by the slaves
addressed during the group command, they all begin executing the command they received.
Figure 27-13 shows an example where this slave is addressed by ADDRESS 1. This slave is addressed after a repeated
START condition. There can be multiple slaves addressed before and after, then at the end of the group command, a
single STOP is generated by the master. At this point a STOP interrupt is asserted.
Figure 27-13.PMBus Group Command Example
27.6.3 Additional Features
27.6.3.1 SMBus
The I
2
C hardware incorporates three hardware SCL low time-outs which allows a time-out to occur for SMBus SCL low
time-out, master extend time-out, and slave extend time-out. These time-outs are driven by the GCLK_SERCOM_SLOW
clock. The GCLK_SERCOM_SLOW clock is used to accurately time the time-out and must be configured to used a
32kHz oscillator. The I
2
C interface also allows for an SMBus compatible SDA hold time.
z T
TIMEOUT
: SCL low time of 25-35 ms. – Measured for a single SCL low period. Enabled by bit
CTRLA.LOWTOUTEN.
S AW
addr[7:0]
A
11110 addr[9:8]
Sr R
S
W
SLAVE ADDRESS
INTERRUPT
S
W
SLAVE ADDRESS
INTERRUPT
11110 addr[9:8]
A
S
A
n Bytes
W
ADDRESS 0
Command/Data
A
Sr
A
n Bytes
W
ADDRESS 1
(this slave)
Command/Data
S
W
SLAVE ADDRESS
INTERRUPT
S
W
SLAVE DATA
INTERRUPT
A
Sr
A
n Bytes
W
ADDRESS 2
Command/Data
P
S
W
SLAVE STOP
INTERRUPT