Cirrus Logic CS42L42 Manual page 53

Fig. 4-23 shows examples of frame organization.
12 MHz, 10 columns, 50 rows, 48 kHz framerate
COL COL COL COL
0 1 2 3
96 kHz
LEFT
2x12
48
kHz
LEFT
1x24
96 kHz
RIGHT
2x12
CMD
1x48
96 kHz
LEFT
2x12
48
kHz
RIGHT
1x24
96 kHz
RIGHT
2x12
GAP 1x2
Rows and columns are numbered from zero upwards. The transmission sequence of bit slots is done by an increasing
order of rows, and, within each row, an increasing order of columns. The bit slots can be identified with a notation of
[<Row>,<Column>]. Thus the first bit of a frame is [0,0], followed by [0,1], [0,2], up to [MaxRow,MaxCol].
The values on successive bit slots form a bit stream that interleaves all of the following:
• Control bits from the master
• Command bits from the master or monitor, and corresponding response bits from slaves or master
• Status bits from the slaves
• Payload data that can be transferred master to slave, slave to master, or slave to slave.
4.8.3 Control Word
A control word occupies the first 48 bits of Column 0 in any frame. Remaining bits of the frame not occupied by the control
word are available for payload data. There are many options for organizing the payload data amongst the various channels
and devices in the system. The control word is a 48-bit field in every SoundWire frame used by the master to read or write
registers, control operations, and query slave status. It also provides frame synchronization information used by the slaves
to keep in sync with the SoundWire Bus. The control word is split into multiple fields.
There are three types of commands:
• Ping—Every slave attached to the bus returns its status. The master sends a ping in any frame that is not performing
a read or write command.
• Write—Writes an 8-bit value from the command owner to one or more registers in one or more devices.
• Read—Reads an 8-bit value from a register in one or more devices.
Each control word field has an owner, defining which device can drive the bus during that bit slot. Some slots have multiple
owners. This multiple ownership uses the modified NRZI scheme to avoid bus contention. For example, if multiple slaves
assert PREQ (ping request, see
on the bus are driving the data to the same value, so there is no contention. Attached slaves not asserting PREQ pass a
Logic 0 symbol by not driving the bus, so there is no contention if other slaves assert PREQ at the same time.
DS1083F2
COL COL COL COL
4 5 6 7
GAP 7x2
192 kHz LEFT
4x6
192 kHz RIGHT
4x6
192 kHz LEFT
4x6
192 kHz RIGHT
4x6
192 kHz LEFT
4x6
192 kHz RIGHT
4x6
192 kHz LEFT
4x6
192 kHz RIGHT
4x6
Figure 4-23. Examples of SoundWire Frame Payload Organization
Table 4-6) to pass a Logic 1 symbol by toggling the data pin in the same bit slot, all drivers
12.288 MHz, 8 columns, 64 rows, 48 kHz framerate
COL COL
COL COL
0 1
8 9
GAP 1x2
48
kHz
LEFT
16
1x24
kHz
3 CH
LEFT
CMD
1x24
1x48
2.4
Mbit
48
PDM
kHz
1x50
RIGHT
1x24
16
kHz
3 CH
8 kHz
RIGHT
16 bits
1x24
6xSTEREO
SYNC
2x16
CS42L42
4.8 SoundWire Interface
COL COL COL COL
2 3 4 5
48 kHz CH1
48 kHz
192 kHz LEFT
16 bits
4x6
STEREO
2x16 192 kHz RIGHT
4x6
48 kHz CH2
96 kHz
192 kHz LEFT
LEFT
4x6
2x12
192 kHz RIGHT
4x6
96 kHz
RIGHT 48 kHz CH3
2x12
192 kHz LEFT
4x6
96 kHz 192 kHz RIGHT
LEFT
4x6
2x12
48 kHz CH4
192 kHz LEFT
96 kHz
4x6
RIGHT
192 kHz RIGHT
2x12
4x6
COL COL
6 7
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