21 I
2
S
21-10
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
Furthermore, the I
2
S provides the status bits FIFOSTAT[2:0]/I2S_FIFO_STAT register that indicate the FIFO
state machine.
5.2 Monitoring the FIFO State Machine
Table 21.
FIFOSTAT[2:0]
State
0x7–0x6
Reserved
0x5
FLUSH: FIFO is flushing the remained audio data before it stops.
0x4
EMPTY: FIFO is empty.
0x3
LACK: FIFO is not full and not empty.
0x2
FULL: FIFO is full.
0x1
INIT:
Initialize all four entries of FIFO.
0x0
STOP: FIFO is idle.
(Default: 0x0)
For more information on FIFOSTAT[2:0], refer to the description of I2S_FIFO_STAT register in Section 21.7.
7. To stop output, write 0 to I2SSTART/I2S_START register.
When I2SSTART is set to 0, the I
2
S module will stop data output after the remaining data stored in the FIFO
are all output. The bit clock is stopped with pulled down to low. The word select clock is also stopped with
pulled down to low if WCLKMD = 0 or pulled up to high if WCLKMD = 1. When the I
2
S stops, I2SBUSY is
reset to 0.
I2SSTART
I2SBUSY
I2S_WS pin
I2S_SCLK pin
I2S_SDO pin
In left or right justified mode
18 bit clock cycles
Valid data
1st L channel
(Dummy)
1st R channel
2nd L channel
Last R channel
Last L channel
18 bit clock cycles 18 bit clock cycles
18 bit clock cycles
I2SSTART
I2SBUSY
I2S_WS pin
I2S_SCLK pin
I2S_SDO pin
In I
2
S mode
Valid data
1st L channel
(Dummy)
1st R channel
2nd L channel
Last R channel
Last L channel
18 bit clock cycles
18 bit clock cycles 18 bit clock cycles
18 bit clock cycles
Conditions: CHMD[1:0] = 0x0 (stereo), WCLKMD = 0 (L ch = low), BCLKPOL = 0 (falling edge),
WSCLKCYC[4:0] = 0x2 (18 clocks)
5.2 Data Output Timing Chart
Figure 21.
*
Output when mute or mono mode is selected
When mute mode is selected using CHMD[1:0]/I2S_CTL register, the I2S_SDO pin is fixed at 0. However, the
FIFO and shift register run the same as stereo mode and three clock signals are output normally. Also in mono
mode, the I2S_SDO pin is fixed at 0 during the output period for the unselected channel. The FIFO data is read
out normally, therefore an interrupt caused by a FIFO empty occurs. If CHMD[1:0] is changed when data is be-
ing output, the mode changes after the current L & R data output has finished.