AN543
Rev. 0.9
23
7.1.1. Common Receiver Commands
Command 0x01 POWER_UP
The POWER_UP command initiates the boot process to move the device from powerdown to powerup mode. The
boot can occur from internal device memory or a system controller downloaded patch. This command powers up
the device with the specified function (FM Receive and AM Receive). Power-up is complete when the CTS bit is
set. This is the only command that may be sent while the device is powered down. Due to variation of the 4 MHz
crystal from vendor to vendor, two power up commands are required for reliably powering up: a 4 MHz crystal pre-
boot POWER_UP command, and a POWER_UP command to boot the part with the desired function (AM, FM).
Command
Bit
7
6
5
4
3
2
1
0
CMD
0x01
ARG1
XSTART[7:0]
ARG2
00
XCLOAD[5:0]
ARG3
CTSIEN
INTSEL
FASTBOOT
00
XIBIAS[2:0]
ARG4
FUNC[3:0] 0000
ARG5
CTEN[4:0]
XMODE[2:0]
ARG
Bit
Name
Function
1
7:0
XSTART[7:0]
Oscillator startup
01110101 = 4 MHz crystal pre-boot (first command in 4 MHz crystal
sequence)
01110111 = boot (normal operation with external clock, or the second
command in a 4 MHz crystal sequence)
2
7:6
Reserved
Always write 00.
2
5:0
XCLOAD[5:0]
Selects the amount of additional on-chip capacitance to be connected
between XTAL1 and gnd and between XTAL2 and gnd. One half of the
capacitance value shown here is the additional load capacitance pre-
sented to the xtal. The minimum step size is 0.25 pF. The required value
will be layout-dependent. Range is 0–0x3F (i.e. 5–20.75 pF) The EVB
sets XCLOAD = 0x27.
3
7
CTSIEN
CTS interrupt enable
0 = Disable.
1 = Enable.
3
6
INTSEL
CTS interrupt pin select
0 = A1 pin.
1 = INTB pin.
3
5
FASTBOOT
Speeds boot time when set. It is required to set this bit with Si475x-A20
and later only.
3
4:3
Reserved
Always write 00.
3
2:0
XBIAS[2:0]
Crystal bias current
3 = 4 MHz crystal or external clock
7 = 4 MHz crystal for boot-up
