GC5316 datasheet(39/75 Pages) TI

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GC5316

SLWS154A − JANUARY 2004 − REVISED MARCH 2004

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The phase of the NCO’s Sin/Cos output can be adjusted relative to the phase of other channel NCOs by specifying

a phase offset. The phase offset is programmed as a 16-bit word, yielding a step size of about 5.5 milliDegrees. The

phase offset word is determine by the following formula:

Phase Offset Word= 216 x Offset_in_Degrees / 360 or,

Phase Offset Word= 216 x Offset_in_Radians / 2

Table 14. Programming

VARIABLE

DESCRIPTION

phase_offset_a(15:0)

16-bit phase offset word for the A signal when in CDMA mode. Also for UMTS mode.

phase_offset_b(15:0)

16-bit phase offset word for the B signal when in CDMA mode. Not used in UMTS mode.

Various synchronization signals are available, which are used to synchronize the NCOs of all channels with respect

to each other. Frequency sync and phase offset sync determine when frequency and phase offset changes occur.

For example, generating a frequency sync after programming the two frequency words causes the NCO (or multiple

NCOs) to change frequency at that time, rather than after each of the three frequency words is programmed over

the control bus. The zero phase sync signal is used to force the sine and cosine oscillators to their zero phase state.

Dither sync can be used to synchronize the dither generators of multiple NCOs. The NCOs used in the transmit

section are identical to what is described for the receive section.

Table 15. Programming

VARIABLE

DESCRIPTION

ssel_nco(2:0)

Sync source for NCO accumulator reset

ssel_dither(2:0)

Sync source for NCO dither reset

ssel_freq(2:0)

Sync source for NCO frequency register loading

ssel_phase(2:0)

Sync source for NCO phase register loading

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