Ameba-D User Manual
User Manual All information provided in this document is subject to legal disclaimers. © REALTEK 2019. All rights reserved.
252
13.2.4.6
NULL DATA Transfer Protocol
NULL DATA transfer is used for some sensors. When IC_DATA_CMD[11] and IC_DATA_CMD[9] is set to 1, I
2
C would ignore REG_IC_TAR but
take the TXFIFO data as slave address. It would only send TXFIFO data in address phase without any further transmission. Fig 13-11 gives the
NULL DATA transfer format.
S
D7
D6
D5
D4
D3
D2
D1
W
ACK
MSB
LSB
Slave Address
Sent by
slave
S = START condition
D = Data write to IC_DATA_CMD
P
Fig 13-11 NULL DATA transfer format
13.2.5
Tx FIFO Management and START, STOP and RESTART Generation
Ameba-D I
2
C does not generate a STOP if the Tx FIFO becomes empty; in this situation the component holds the SCL line low, stalling the bus
until a new entry is available in the Tx FIFO. A STOP condition is generated only when the user specifically requests it by setting bit 9 (Stop bit)
of the command written to REG_IC_DATA_CMD register. Fig 13-12 shows the fields in IC_DATA_CMD. Please refer to the register description
for more detail information.
RESTART
STOP
CMD
DATA
REG_IC_DATA_CMD
7
0
8
9
10
Reserved
15
11
NULL_DAT
12
Fig 13-12 IC_DATA_CMD register content
Fig 13-13 illustrates the behavior of the I
2
C when the Tx FIFO becomes empty while operating as a master transmitter, as well as showing the
generation of a STOP condition.
A
6
A
5
A
4
A
3
A
2
A
1
A
0
ACK
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
7
ACK
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
7
ACK
W
D
6
D
5
D
4
D
3
D
2
D
1
D
0
D
7
ACK
SDA
SCL
FIFO
EMPTY
SDA
SCL
FIFO
EMPTY
Data written
into Tx FIFO
S
P
Data availability makes
START condition
Master holds SCL low since STOP
bit is NOT set in the last data
Last data in FIFO and
STOP bit not set
New data
written into
Tx FIFO
Last data in FIFO
and STOP bit is set
STOP bit in the last data
makes STOP condition on bus
Master makes SCL
continue when data
available
Fig 13-13 Master transmitter — Tx FIFO empties/STOP generation
Fig 13-14 illustrates the behavior of the I
2
C when the Tx FIFO becomes empty while operating as a master receiver, as well as showing the
generation of a STOP condition.
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2019-05-15 10:08:03