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Lucent Technologies Inc.
53
Advance Data Sheet
B900
July 1999
Baseband Signal Processor
5 Software Architecture (continued)
5.2
Register Settings (continued)
Table 41. clkc Register Fields
Bit
15—13
12
11—8
7—6
5—4
3
2
1
0
Field
Res
PFIVOLT DOUT MUX
SLOMUX
SELCLK
STOPCLK
ROSCDIS
OSCDIS
PLLEN
Bit
Field
Description
15—13
Reserved
Write with 0, read as 0.
12
PFIVOLT
Voltage select:
0 = 3 V.
1 = 5 V.
11—8
DOUT MUX[3:0]
DOUT source selection:
0000 = logic 0 selected to DOUT.
0001 = input crystal/clock (CLKIN) selected to DOUT.
0010 = low-frequency clock (CLKLOW) selected to DOUT.
0011 = wait-stated B900 clock (CLKWAIT) selected to DOUT.
0100 = free-running B900 clock (CLKFREE) selected to DOUT.
0101 = slow, smooth MUX output selected to DOUT (CLKCORE2X).
0110 = logic 0 selected to DOUT.
0111 = logic 1 selected to DOUT.
7—6
SLOMUX[1:0]
Low-frequency clock source selection (CLKLOW):
00 = chip input clock (CLKIN) divided by 4.
01 = chip input clock (CLKIN) divided by 32.
10 = chip input clock (CLKIN) divided by 128.
11 = internal ring oscillator (CLKRING).
5—4
SELCLK[1:0]*
* It is recommended that the 2 bits of the SELCLK field be changed one at a time to prevent the possibility of an intermediate clock switch
before switching to the desired destination clock. For example, to switch the clock selection back and forth between the low-frequency clock
(CLKLOW) and the high-frequency PLL output (CLKPLL), the more significant bit of SELCLK (clkc[5]) should be set to one, allowing the less
significant bit of SELCLK (clkc[4]) to be toggled on and off without the possibility of an intermediate clock switch.
Select the 2X core clock (CLKCORE2X) (as long as STOPCLK = 0):
00 = select input clock (CLKIN).
X1 = select PLL output (CLKPLL).
10 = select low-frequency clock (CLKLOW) as selected by SLOMUX[1:0].
3
STOPCLK
Stop B900 core clock (CLKCORE2X):
0 = clock runs as normal.
1 = disable 2X B900 input core clock.
2
ROSCDIS
Ring oscillator disable:
0 = enable the internal ring oscillator clock (CLKRING).
1 = disable the internal ring oscillator clock (CLKRING).
1
OSCDIS
This bit should not be set if the internal crystal oscillator is bypassed, i.e., OSCBYP pin = 1. Also note that when this bit is set, it will not take
effect until after CLKRING is selected and is sourcing CLKCORE2X.
Oscillator disable (this bit should only be set if the oscillator is not bypassed,
i.e., OSCBYP pin = 0):
0 = enable the crystal oscillator clock.
1 = disable the crystal oscillator clock.
0
PLLEN
This bit is overridden if it is cleared to zero and if the PLL output (CLKPLL) is selected as the 2X core clock (if SELCLK[0] = 1).
Phase-locked loop enable:
0 = disable PLL circuitry.
1 = enable PLL to operate.