wm8594seft-v Wolfson Microelectronics plc, wm8594seft-v Datasheet - Page 18

• Manufacturer Part Number: wm8594seft-v
• Description: 24-bit 192khz 2vrms Multi-channel Codec
• Manufacturer: Wolfson Microelectronics plc

WM8594
CONTROL INTERFACE
2-WIRE (SM-BUS COMPATIBLE) SERIAL CONTROL INTERFACE MODE
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Control of the WM8594 is achieved by a 2-wire SM-bus-compliant or 3-wire SPI compliant serial
interface with readback. Software interface mode is selected using the MODE pin as shown in Table
8 below:
Table 8 Control Interface Mode Selection
Many devices can be controlled by the same bus, and each device has a unique 7-bit address.
REGISTER WRITE
The controller indicates the start of data transfer with a high to low transition on SDIN while SCLK
remains high. This indicates that a device address and data will follow. All devices on the 2-wire bus
respond to the start condition and shift in the next eight bits on SDIN (7-bit address and read/write
bit, MSB first). If the device address received matches the address of the WM8594, the WM8594
responds by pulling SDIN low on the next clock pulse (ACK). If the address is not recognised, the
WM8594 returns to the idle condition and waits for a new start condition with valid address.
When the WM8594 has acknowledged a correct address, the controller sends the first byte of control
data (B23 to B16, i.e. the WM8594 register address). The WM8594 then acknowledges the first data
byte by pulling SDIN low for one SCLK pulse. The controller then sends a second byte of control
data (B15 to B8, i.e. the first 8 bits of register data), and the WM8594 acknowledges again by pulling
SDIN low for one SCLK pulse. Finally, the controller sends a third byte of control data (B7 to B0, i.e.
the final 8 bits of register data), and the WM8594 acknowledges again by pulling SDIN low for one
SCLK pulse.
The transfer of data is complete when there is a low to high transition on SDIN while SCLK is high.
After receiving a complete address and data sequence the WM8594 returns to the idle state and
waits for another start condition. If a start or stop condition is detected out of sequence at any point
during data transfer (i.e. SDIN changes while SCLK is high), the WM8594 reverts to the idle
condition.
The WM8594 device 2-wire write address is 34h (00110100) or 36h (00110110), selectable by
control of /CS.
Table 9 2-Wire Control Interface Bus Address Selection
Figure 7 2-Wire Write Protocol
/CS (PIN 45)
MODE
High
Low
0
1
INTERFACE FORMAT
2-WIRE BUS ADDRESS (B[7:1])
2 wire
3 wire
34h (0011010)
36h (0011011)
PD Rev 4.1 July 2008
Production Data
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