z87200 ZiLOG Semiconductor, z87200 Datasheet - Page 42

• Manufacturer Part Number: z87200
• Description: Spread-spectrum Transceiver
• Manufacturer: ZiLOG Semiconductor

CONTROL REGISTERS (Continued)
Z87200
Spread-Spectrum Transceiver
Address 4C
Data Symbol Code
Addresses 4C
code sequence values. The storage capacity, assign-
ments, and operation are similar to that of the Acquisi-
tion/Preamble PN code sequence values. The configura-
tion of the bits stored is as shown in Table 22.
Transmit Control Registers
Address 54
Bits 1-0 — Transmitter Overlay Select
The Z87200 incorporates programmable overlay code
generators in both the transmitter and receiver. When en-
abled, the selected transmitter overlay code is subtracted
from the data symbols, one overlay bit per symbol in both
BPSK and QPSK modes. No synchronization is required
since the codes in both the transmitter and the receiver are
automatically synchronized by resetting the code genera-
tors at the start of each burst. The addition of the overlay
codes randomizes the transmitted data sequence to guar-
antee that the spectrum of the transmitted signal will be ad-
equately whitened and will not contain a small number of
spectral lines even when the data itself is not random.
Three transmit and receive overlay codes can be selected,
where they are each maximal length sequences with
lengths of 63, 511 and 1023 symbols. The transmitter
overlay codes are enabled and selected by the settings of
bits 1-0 of address 54
4-40
H
H
Table 22. Data Symbol Codes
:
H
through 53
to 53
Addr 4D
Addr 4C
Addr 53
Code Bits 63-56
H
Code Bits 15-8
Code Bits 7-0
H
contain the binary Data Symbol PN
, as shown in Table 23.
••••••••••
••••••••••
H
H
:
H
H
, Bits 7-0
, Bits 7-0
, Bits 7-0
PS010202-0601
Bit 2 —Transmitter Symbols Per Burst Off
Bit 2 of address 54
low (0).
Address 55
Transmitter Data Symbols per Burst (bits 15-0)
The data stored as two bytes in addresses 55
and 56
burst for the transmitter. This unsigned value must range
from 1 to 65,535 (0001
data symbols per burst will be this value plus 1. Note that
the range is slightly different from that in the receiver. Once
the number of transmitted data symbols exceeds this num-
ber, the burst is assumed to have ended and the transmit-
ter is immediately turned off. If the data value is set to
0000
mitting the Z87200 to be used for continuous transmission
of data.
Bits 1-0 in
Addr. 54
H
Table 23. Transmitter Overlay Code Select
, then the symbols per burst counter is disabled, per-
H
(MS byte) defines the number of data symbols per
0
1
2
3
H
H
through 56
H
is not used and must always be set
H
1023: 1+x
H
Overlay Code Disabled
to FFFF
Overlay Code Length
511: 1+x
:
63: 1+x
and Polynomial
-2
H
-2
-2
), and the number of
+x
+x
+x
-3
-3
-3
+x
+x
+x
-5
-5
-5
+x
+x
+x
H
-6
-9
-10
(LS byte)
Zilog