AN332
Confidential Rev. 0.2
19
Command 0x32. TX
_
TUNE
_
MEASURE (Si4712/13/20/21 Only)
Enters receive mode (disables transmitter output power) and measures the received noise level (RNL) in units of
dBµV on the selected frequency. The command sets the tuning frequency between 76 and 108 MHz in 10 kHz
units and steps of 50 kHz. For example 76.05 MHz = 7605 is valid because it follows the 50 kHz step requirement
but 76.01 MHz = 7601 is not valid. The command also sets the antenna tuning capacitance. A value of 0 indicates
autotuning, and a value of 1–191 indicates a manual override. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. The ERR bit (and optional interrupt) is set if an invalid argument is sent. Note that
only a single interrupt occurs if both the CTS and ERR bits are set. The optional STC interrupt is set when the
command completes. The STCINT bit is set only after the GET_INT_STATUS command is called. This command
may only be sent when in powerup mode. The command clears the STC bit if it is already set. See Figure 17, “CTS
and STC Timing Model,” on page 187 and Table 41, “Command Timing Parameters for the FM Transmitter,” on
page 188.
Command arguments: Three
Response bytes: None
Command
Response
Bit
D7
D6
D5
D4
D3
D2
D1
D0
CMD
0
0
1
1
0
0
1
0
ARG1
0
0
0
0
0
0
0
0
ARG2
FREQ
H
[7:0]
ARG3
FREQ
L
[7:0]
ARG4
ANTCAP[7:0]
ARG
Bit
Name
Function
1
7:0
Reserved
Always write to 0.
2
7:0
FREQ
H
[7:0]
Tune Frequency High Byte.
This byte in combination with FREQ
L
selects the tune frequency in units of
10 kHz. In FM mode the valid range is from 7600 to 10800 (76–108 MHz).
The frequency must be a multiple of 50 kHz.
3
7:0
FREQ
L
[7:0]
Tune Frequency Low Byte.
This byte in combination with FREQ
H
selects the tune frequency in units of
10 kHz. In FM mode the valid range is from 7600 to 10800 (76–108 MHz).
The frequency must be a multiple of 50 kHz.
4
7:0
ANTCAP[7:0]
Antenna Tuning Capacitor.
This selects the value of the antenna tuning capacitor manually, or auto-
matic if set to zero. The valid range is 0–191.
Bit
D7
D6
D5
D4
D3
D2
D1
D0
STATUS
CTS
ERR
X
X
X
RDSINT
ASQINT
STCINT