Datasheet

Register Read/Write Operation
MSB
LSB
RegisterIndex(or Address)
RegisterData
R/W
IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 D7 D6 D5 D4 D3 D2 D1 D0
HighImpedance
WhenReadModeisInstructed
R/W
A6
MS
MC
MDI
MDO
A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
D7
D6 D5
D4
D3
D2 D1
D0
PCM1795
SLES248 – MAY 2009 ........................................................................................................................................................................................................ www.ti.com
All read/write operations for the serial control port use 16-bit data words. Figure 41 shows the control data word
format. The most significant bit (MSB) is the read/write (R/ W) bit. For write operations, the R/ W bit must be set to
'0'. For read operations, the R/ W bit must be set to '1'. There are seven bits, labeled IDX[6:0], that hold the
register index (or address) for the read and write operations. The least significant eight bits, D[7:0], contain the
data to be written to, or the data that was read from, and the register specified by IDX[6:0].
Figure 42 shows the functional timing diagram for writing or reading the serial control port. MS is held at a logic 1
state until a register must be written to or read from. To start the register write or read cycle, MS is set to logic 0.
Sixteen clocks are then provided on MC, corresponding to the 16 bits of the control data word on MDI and
readback data on MDO. After the eighth clock cycle has completed, the data from the indexed-mode control
register appears on MDO during the read operation. After the 16th clock cycle has completed, the data are
latched into the indexed-mode control register during the write operation. To write or read subsequent data, MS
must be set to '1' once.
Figure 41. Control Data Word Format for MDI
NOTE: Bit 15 is used for selection of write or read. Setting R/ W = 0 indicates a write, while R/ W = 1 indicates a read. Bits 14 – 8 are used for
the register address. Bits 7 – 0 are used for register data.
Figure 42. Serial Control Format
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