Modem Modes of Operation
MC1321x Reference Manual, Rev. 1.6
Freescale Semiconductor
7-19
– Integer lo1_idiv[7:0] = N
hex
– Fractional lo1_num[15:0] is found by converting the decimal fraction to a 16-bit
hexadecimal fraction -
frac
dec
= lo1_num
dec
/ 65536 or
lo1_num
dec
= 65536 * frac
dec
then,
lo1_num[15:0] = lo1_num
hex
As an example use Channel 23 (desired frequency is 2465 MHz):
([N+1].frac)
dec
= 2465 MHz / 16 MHz = 154.0625
– N+1 = 154
dec
and N = 153
dec
, therefore, lo1_idiv[7:0] = 0x99
– lo1_num
dec
= 65536 * 0.0625 = 4096
dec
, therefore, lo1_num[15:0] = 0x1000
The channels and the respective required bit values of the integer settings LO1_Int_Div Register 0F, Bits
7-0 (lo1_idiv[7:0]) and the fractional settings LO1_Num Register 10 (lo1_num[15:0]) are shown in
.
7.5
Transmit Power Adjustment
The PA output power can be controlled via programming of the PA_Lvl Register 12[7:0], whose fields
include pa_lvl_course[1:0], pa_lvl_fine[1:0], pa_dr_coarse[1:0], and pa_dr_fine[1:0]. The programmable
range of differential power is typically -27 dBm to +3 dBm.
versus SPI register settings for PA_Lvl Register 12[7:0].
NOTE
Register12[7:0] value of 0xBC is the default setting and yields a nominal
power out of -1 dBm to 0 dBm. Also, common practice is to allow Register
12[3:0] to stay at its default value of 0xC and only adjust the pa_lvl_coarse
and pa_lvl_fine fields as required; this allows a range of about -16 dBm to
+1.4 dBm.
Table 7-3. MC1321x Power Output vs. SPI Settings (Register 12)
PA Power Adjust
Reg 12[7:0]
(Hex)
Typical Differential Power at
Output Contact (dBm)
Typical PA Current
(mA)
Comments
00
-28.7
20.9
04
-22.0
21.7
08
-18.5
22.9
0C
-16.2
25.0
Reg 12[3:0] default
1C
-15.9
25.1
Reg 12[3:0] default
2C
-15.3
25.1
Reg 12[3:0] default
3C
-14.8
25.1
Reg 12[3:0] default
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