Z87200 datasheet(21/54 Pages) ZILOG

21 / 54 page

Z87200

Zilog

Spread-Spectrum Transceiver

DS96WRL0400

4-21

The factor of 1/4 results from truncation of the 2 LSBs of

the signal in the integrator path of the loop so that, when

added to the signal in the direct path, the LSBs of the sig-

nals are aligned. The coefficients K1 and K2 are defined by

the data stored in bits 4-0 of addresses 35H and 34H, re-

spectively. In addition, bit 5 of addresses 35H and 34H con-

trol whether the K1 and K2 paths, respectively, are en-

abled. These parameters thus give the user full control of

the Loop Filter characteristics.

RXIIN7-0 (Pins 91-98)

Receiver In-Phase Input. RXIIN is an 8-bit input port for

in-phase data from external A/D converters. Data may be

received in either two’s complement or offset binary format

as selected by bit 3 of address 01H. The sampling rate of

the RXIIN signals (the I.F. sampling rate of the A/Ds) may

be independent of the baseband sampling rate (the Down-

converter integrate and dump rate) and the PN chip rate,

but must be equal to RXIFCLK and at least two times

greater than the baseband sampling rate. Since the base-

band sampling rate must be set at twice the PN chip rate,

the I.F. sampling rate must thus be at least four times the

PN chip rate. Data on the pins is latched and processed by

RXIFCLK.

RXQIN7-0 (Pins 2-9)

Receiver Quadrature-Phase Input. RXQIN is an 8-bit in-

put port for quadrature-phase data from external A/D con-

verters. Data may be received in either two’s complement

or offset binary format as selected by bit 3 of address 01H.

As with RXIIN, the sampling rate of the RXQIN signals may

be independent of the baseband sampling and PN chip

rates in the receiver, but must be at least two times greater

than the baseband sample rate (or, equivalently, at least

four times greater than the PN chip rate). Data on the pins

is latched and processed by RXIFCLK.

Figure 9. Frequency Discriminator and Loop Filter Detail

Z87200 Datasheet(PDF) 21 Page - Zilog, Inc.