SI570 Datasheet, PDF (15/26 Pages) Silicon Laboratories – ANY-RATE I2C PROGRAMMABLE XO/VCXO

Si570/Si571
Register 7. High Speed/N1 Dividers
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
HS_DIV[2:0]
N1[6:2]
Type
R/W
R/W
Bit
Name
Function
7:5 HS_DIV[2:0] DCO High Speed Divider.
Sets value for high speed divider that takes the DCO output f_OSC as its clock input.
000 = 4
001 = 5
010 = 6
011 = 7
100 = Not used.
101 = 9
110 = Not used.
111 = 11
4:0
N1[6:2]
CLKOUT Output Divider.
Sets value for CLKOUT output divider. Allowed values are [1] and [2, 4, 6, ..., 2⁷]. Illegal
odd divider values will be rounded up to the nearest even value. The value for the N1 reg-
ister can be calculated by taking the divider ratio minus one. For example, to divide by 10,
write 0001001 (9 decimal) to the N1 registers.
0000000 = 1
1111111 = 2⁷
Register 8. Reference Frequency
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
N1[1:0]
RFREQ[37:32]
Type
R/W
R/W
Bit
Name
Function
7:6
N1[1:0]
CLKOUT Output Divider.
Sets value for CLKOUT output divider. Allowed values are [1, 2, 4, 6, ..., 2⁷]. Illegal odd
divider values will be rounded up to the nearest even value. The value for the N1 regis-
ter can be calculated by taking the divider ratio minus one. For example, to divide by
10, write 0001001 (9 decimal) to the N1 registers.
0000000 = 1
1111111 = 2⁷
5:0 RFREQ[37:32] Reference Frequency.
Frequency control input to DCO.
Rev. 0.3
15