si4021 Silicon Laboratories, si4021 Datasheet - Page 23

• Manufacturer Part Number: si4021
• Description: Si4021 Universal Ism Band Fsk Transmitter
• Manufacturer: Silicon Laboratories

Push-button 1:
Short Explanation:
Note:
RX-TX ALIGNMENT PROCEDURES
RX-TX frequency offset can be caused only by the differences in the actual reference frequency. To minimize these errors it is suggested to
use the same crystal type and the same PCB layout for the crystal placement on the RX and TX PCBs.
To verify the possible RX-TX offset it is suggested to measure the CLK output of both chips with a high level of accuracy. Do not measure the
output at the XTL pin since the measurement process itself will change the reference frequency. Since the carrier frequencies are derived
from the reference frequency, having identical reference frequencies and nominal frequency settings at the TX and RX side there should be
no offset if the CLK signals have identical frequencies.
It is possible to monitor the actual RX-TX offset using the AFC status report included in the status byte of the receiver. By reading out the
status byte from the receiver the actual measured offset frequency will be reported. In order to get accurate values the AFC has to be
disabled during the read by clearing the "en" bit in the AFC Control Command (bit 0).
00000080
00000090
000000A0
000000B0
000000C0
000000D0
000000E0
000000F0
Address
86–E5
E6–E7
80–81
82–83
84–85
This routine is repeatedly executed while PB1 is pressed, because continuous execution was selected at POR (CA1E code issued in
the power-on reset section before).
88
55
55
55
55
55
55
00
Command
72
55
55
55
55
55
55
00
C6
C4
8
A
A6
55
55
55
55
55
55
00
10
55
55
55
55
55
55
00
Parameter
60x55
C6
55
55
55
55
55
55
00
872
610
60
00
55
55
55
60
55
55
55
00
C4
55
55
55
55
55
55
00
Related Control Command
Configuration Control
Frequency
Data Transmit
Sleep
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
Remarks
433MHz band, Xtal C
f
f
Transmit the next 96 bytes
Data
Power down, go to address 80
dev
c
=(43+1552/4000)*10MHz
=90kHz
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
55
55
55
55
55
55
00
00
L
=12pF
55
55
55
55
55
55
00
00
IA4221
23