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WM8214

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PP Rev 1.6 March 2004

21

SERIAL INTERFACE: REGISTER READ-BACK

Figure 16 shows register read-back in serial mode. Read-back is initiated by writing to the serial bus

as described above but with address bit a4 set to 1, followed by an 8-bit dummy data word. Writing

address (a5, 1, a3, a2, a1, a0) will cause the contents (d7, d6, d5, d4, d3, d2, d1, d0) of

corresponding register (a5, 0, a3, a2, a1, a0) to be output MSB first on pin SDO (on the falling edge

of SCK). Note that pin SDO is shared with an output pin, OP[7], therefore OEB should always be

held low and the OPD register bit should be set low when register read-back data is expected on this

pin. The next word may be read in to SDI while the previous word is still being output on SDO.

SCK

SEN

SDI

a5

1

a3 a2 a1 a0

x

x

xxx

xxx

Address

Data Word

d7 d6 d5 d4 d3 d2 d1 d0

Output Data Word

SDO/

OP[7]

OEB

Figure 16 Serial Interface Register Read-back