TAS5705
SLOS549–JUNE 2008...................................................................................................................................................................................................... www.ti.com
I2C SERIAL CONTROL INTERFACE
The TAS5705 DAP has a bidirectional I2C interface that is compatible with the I2C (Inter IC) bus protocol and
supports both 100-kHz and 400-kHz data transfer rates for single- and multiple-byte write and read operations.
This is a slave-only device that does not support a multimaster bus environment or wait-state insertion. The
control interface is used to program the registers of the device and to read device status.
The DAP supports standard-mode I2C bus operation (100 kHz maximum) and fast I2C bus operation (400 kHz
maximum). The DAP performs all I2C operations without I2C wait cycles.
General I2C Operation
The I2C bus employs two signals, SDA (data) and SCL (clock), to communicate between integrated circuits in a
system. Data is transferred on the bus serially, one bit at a time. The address and data can be transferred in byte
(8-bit) format, with the most significant bit (MSB) transferred first. In addition, each byte transferred on the bus is
acknowledged by the receiving device with an acknowledge bit. Each transfer operation begins with the master
device driving a start condition on the bus and ends with the master device driving a stop condition on the bus.
The bus uses transitions on the data terminal (SDA) while the clock is high to indicate start and stop conditions.
A high-to-low transition on SDA indicates a start, and a low-to-high transition indicates a stop. Normal data-bit
transitions must occur within the low time of the clock period. These conditions are shown in Figure 37. The
master generates the 7-bit slave address and the read/write (R/W) bit to open communication with another
device and then waits for an acknowledge condition. The TAS5705 holds SDA low during the acknowledge clock
period to indicate an acknowledgment. When this occurs, the master transmits the next byte of the sequence.
Each device is addressed by a unique 7-bit slave address plus R/W bit (1 byte). All compatible devices share the
same signals via a bidirectional bus using a wired-AND connection. External pullup resistors must be used to set
the high level for the SDA and SCL signals.
8-Bit Register Data For
Address (N)
8-Bit Register Data For
Address (N)
R/
W
8-Bit Register Address (N)
7-Bit Slave Address
A
A
A
A
SDA
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
SCL
Start
Stop
T0035-01
Figure 37. Typical I2C Sequence
There is no limit on the number of bytes that can be transmitted between start and stop conditions. When the last
word transfers, the master generates a stop condition to release the bus. A generic data transfer sequence is
shown in Figure 37.
The 7-bit address for TAS5705 is 0011 011 (0x36).
Single- and Multiple-Byte Transfers
The serial control interface supports both single-byte and multiple-byte read/write operations for status registers
and the general control registers associated with the PWM. However, for the DAP data processing registers, the
serial control interface supports only multiple-byte (4-byte) read/write operations.
During multiple-byte read operations, the DAP responds with data, a byte at a time, starting at the subaddress
assigned, as long as the master device continues to respond with acknowledges. If a particular subaddress does
not contain 32 bits, the unused bits are read as logic 0.
During multiple-byte write operations, the DAP compares the number of bytes transmitted to the number of bytes
that are required for each specific subaddress. If a write command is received for a biquad subaddress, the DAP
expects to receive five 32-bit words. If fewer than five 32-bit data words have been received when a stop
command (or another start command) is received, the data received is discarded. Similarly, if a write command is
received for a mixer coefficient, the DAP expects to receive one 32-bit word.
32
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TAS5705
TI [ TEXAS INSTRUMENTS ]
