AS3693C-9 Datasheet, PDF (20/30 Pages) ams AG – SPI interface

AS3693C
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The word address transfer is initiated with a START condition issued by the master while the bus is idle. The
START condition is followed by the device-write address and the word address.
In order to change the data direction a repeated START condition is issued on the 1^st SCL pulse after the
acknowledge bit of the word address transfer. After the reception of the device-read address, the slave becomes
the transmitter. In this state the slave transmits register data located by the previous received word address
vector. The master responds to the data byte with a not-acknowledge, and issues a STOP condition on the bus.
Figure 4 – I²C Sequential-Read:
S
DW
A
WA
A Sr
DR
A data 1 A data 2
…
A data n N P
read register
WA++
WA++
Sequential-Read is the extended form of Random-Read, as more than one register-data bytes are transferred
subsequently. In difference to the Random-Read, for a sequential read the transferred register-data bytes are
responded by an acknowledge from the master. The number of data bytes transferred in one sequence is
unlimited (consider the behavior of the word-address counter). To terminate the transmission the master has to
send a not-acknowledge following the last data byte and generate the STOP condition subsequently.
Figure 5 – I²C Current-Address-Read:
S
DR
A data 1 A data 2
…
A data n N P
read register
WA++
read register
WA++
read register
WA++
WA++
To keep the access time as small as possible, this format allows a read access without the word address transfer
in advance to the data transfer. The bus is idle and the master issues a START condition followed by the Device-
Read address. Analogous to Random-Read, a single byte transfer is terminated with a not-acknowledge after the
1^st register byte. Analogous to Sequential-Read an unlimited number of data bytes can be transferred, where the
data bytes has to be responded with an acknowledge from the master. For termination of the transmission the
master sends a not-acknowledge following the last data byte and a subsequent STOP condition.
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Revision 1.4 / 2009-08-13
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