Cirrus-logic CS42L73 User Manual download pdf (Page 73)

DS882F1 73

CS42L73

If a read address different from that which is based on the last received MAP address is desired, an abort-

ed write operation can be used as a preamble that sets the desired read address. This preamble tech-

nique is illustrated in Figure 39. In the figure, a write operation is aborted (after the acknowledge for the

MAP byte) by sending a stop condition.

The following pseudocode illustrates an aborted write operation followed by a single read operation. For

multiple read operations, autoincrement would be set on (as is shown in Figure 39).

Send start condition.

Send 10010100 (chip address and write operation).

Receive acknowledge bit.

Send MAP byte, autoincrement off.

Receive acknowledge bit.

Send stop condition, aborting write.

Send start condition.

Send 10010101 (chip address and read operation).

Receive acknowledge bit.

Receive byte, contents of selected register.

Send acknowledge bit.

Send stop condition.

4.17 Fast Start Mode

Using fast start mode can reduce the transition time from a low power state to producing audio in the default

power-up sequence (“Power-Up Sequence (xSP to HP/LO)” on page 66) to meet stricter requirements. See

Table 13 for typical power up times for normal mode and fast start mode. See “Startup Times” on page 133

for setup conditions.

Also, a system may want the CS42L73 to be in a low power state but still needs the MIC2_SDET

micro-

phone button short detection to function as a system wake feature. In this case, reducing the MCLK frequen-

cy will help to lower the power consumption without affecting audio performance since all of the ADCs and

DACs are powered down. To support this power state, fast start mode needs to be enabled to properly de-

tect microphone button presses with a slow MCLK frequency.

Table 13. Start Up Times

Output Path Normal Mode Fast Start Mode Unit

HPOUT/LINEOUT 70 30 ms

EAR SPKOUT 46 35 ms

SPKOUT/SPKLINEOUT 140 45 ms

SCL

CHIP ADDRESS (WRITE) MAP BYTE DATA

START

ACK

STOP

ACK

ACKACK

SDA

7 0 7 0

CHIP ADDRESS (READ)

START

7 6 5 4 3 2 1 0

7 0

16 8 9 12 13 14 15 4 5 6 7 0 1 20 21 22 23 24

26 27 28

2 3 10 11 17 18 19 25

ACK

STOP

MAP Addr = Z

INCR = 1

Slave Addr = 1001010

7 6 5 4 3 2 1 0

R/W = 0

Slave Addr = 1001010

7 6 5 4 3 2 1 0

R/W = 1

DATA DATA

Data from Addr Z

Data from Addr Z+1

Data from Addr Z+n

SDA

Source

Master Master Master

Pullup

Slave Slave

Slave Slave Slave

Master Master Master

Pullup

Figure 39. Control Port Timing, I²C Reads with Preamble and Autoincrement

1 2 ... 68 69 70 71 72 73 74 75 76 77 78 ... 138 139

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