3–4

DOUT

DOUT

DIN

DAC Data In

ADC Data

Out

DAC Data In

All Bits 0

Secondary

Update

16 SCLKs

64 FCLKs

16 SCLKs

16 SCLKs

FS

FC

(Secondary

Read)

(Secondary

Read or Write)

Communication Frame 1 (CF1)

(CF2)

No Secondary

Request

ADC Data

Out

ADC Data

Out

ADC Data

Out

(Secondary

Write)

Primary

Secondary

Primary

64 FCLKs

Register

Data

8 SCLKs

32 FCLKs

Figure 3–3. Hardware FC Secondary Request

(Phone Mode Disabled)

In Figure 3–4, FC hardware terminal 15 is left in its unasserted state (0). FC is asserted through software

by embedding an asserted high level (1) in the LSB of the 16-bit primary word. This is possible when not

in 16-bit mode (Control 1 register, bit 2 = 0) because the user is using only 15 bits of DAC information.