DS3106
47
Register Name:
ICR3, ICR4
Register Description:
Input Configuration Register 3, 4
Register Address:
22h, 23h
Bit #
7
6
5
4
3
2
1
0
Name
DIVN
LOCK8K
—
FREQ[3:0]
Default
0
see below
Note: These registers are identical in function. ICRx is the control register for input clock ICx.
Bit 7: DIVN Mode (DIVN). When DIVN is set to 1 and LOCK8K = 0, the input clock is divided down by a
programmable predivider. The resulting output clock is then passed to the DPLL. All input clocks for which DIVN =
1 are divided by the factor specified in
DIVN1 and
DIVN2. When DIVN = 1 and LOCK8K = 0 in an
ICR register, the
FREQ field of that register must be set to the input frequency divided by the divide factor. When DIVN = 1 and
LOCK8K = 1 in an
ICR register, the FREQ field of that register is decoded as the alternate frequencies. See
0 = Disabled
1 = Enabled
Bit 6: LOCK8K Mode (LOCK8K). When LOCK8K is set to 1 and DIVN = 0, the input clock is divided down by a
preset predivider. The resulting output clock, which is always 8kHz, is then passed to the DPLL. LOCK8K is
ignored when DIVN = 0 and FREQ[3:0] = 1001 (2kHz) or 1010 (4kHz). When DIVN = 1 and LOCK8K = 1 in an
ICRregister, the FREQ field of that register is decoded as the alternate frequencies. See Sections
7.4.2.2 and
7.4.2.30 = Disabled
1 = Enabled
Bits 3 to 0: Input Clock Frequency (FREQ[3:0]). When DIVN = 0 and LOCK8K = 0 (standard direct-lock mode),
this field specifies the input clock’s nominal frequency for direct-lock operation. When DIVN = 0 and LOCK8K = 1
(LOCK8K mode), this field specifies the input clock’s nominal frequency for LOCK8K operation. When DIVN = 1
and LOCK8K = 0 (DIVN mode), this field specifies the frequency after the DIVN divider (i.e., input frequency
divided by
DIVN + 1). When DIVN = 1 and LOCK8K = 1 (alternate direct-lock frequencies), this field specifies the
input clock’s nominal frequency for direct-lock operation.
DIVN = 0 or LOCK8K = 0: (Standard direct-lock mode, LOCK8K mode, or DIVN mode)
0000 = 8kHz
0001 = 1544kHz or 2048kHz (as determined by SONSDH bit in the
MCR3 register)
0010 = 6.48MHz
0011 = 19.44MHz
0100 = 25.92MHz
0101 = 38.88MHz
0110 = 51.84MHz
0111 = 77.76MHz
1000 = 155.52MHz (only valid for LVDS inputs)
1001 = 2kHz
1010 = 4kHz
1011 = 6312kHz
1100 = 5MHz
1101 = 31.25 MHz (not a multiple of 8 kHz and therefore not valid for LOCK8K mode)
1110–1111 = undefined
DIVN = 1 and LOCK8K = 1: (Alternate direct-lock frequency decode)
0000 = 10MHz (internally divided down to 5MHz)
0001 = 25MHz (internally divided down to 5MHz)
0010 = 62.5MHz (internally down to 31.25MHz)
0011 = 125MHz (internally down to 31.25MHz)
0101–1111 = undefined
FREQ[3:0] Default Values: