National CP3BT26 - Manual (Page 55)

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CP3
BT26
FCLK bit cannot be cleared until the PLL clock
has stabilized. After reset this bit is set.
0
– PLL is active.
1 – PLL is powered down.
ACE1 When the Auxiliary Clock Enable bit is set and
a stable Main Clock is provided, the Auxiliary
Clock 1 prescaler is enabled and generates
the first Auxiliary Clock. When the ACE1 bit is
clear or the Main Clock is not stable, Auxiliary
Clock 1 is stopped. Auxiliary Clock 1 is used
as the clock input for the Bluetooth LLC and
the Advanced Audio Interface. After reset this
bit is clear.
0
– Auxiliary Clock 1 is stopped.
1 – Auxiliary Clock 1 is active if the Main
Clock is stable.
ACE2 When the Auxiliary Clock Enable 2 bit is set
and a stable Main Clock is provided, the Aux-
iliary Clock 2 prescaler is enabled and gener-
ates Auxiliary Clock 2. When the ACE2 bit is
clear or the Main Clock is not stable, the Aux-
iliary Clock 2 is stopped. Auxiliary Clock 2 is
used as the clock input for the CVSD/PCM
transcoder and the A/D converter. After reset
this bit is clear.
0
– Auxiliary Clock 2 is stopped.
1 – Auxiliary Clock 2 is active if the Main
Clock is stable.
POR Power-On-Reset - The Power-On-Reset bit is
set when a power-turn-on condition has been
detected. This bit can only be cleared by soft-
ware, not set. Writing a 1 to this bit will be ig-
nored, and the previous value of the bit will be
unchanged.
0
– Software cleared this bit.
1 – Software has not cleared his bit since the
last reset.
11.9.2 High Frequency Clock Prescaler Register
(PRSFC)
The PRSFC register is a byte-wide read/write register that
holds the 4-bit clock divisor used to generate the high-fre-
quency clock. In addition, the upper three bits are used to
control the operation of the PLL. The register is initialized to
4Fh at reset (except in PROG mode
.)
FCDIV The Fast Clock Divisor specifies the divisor
used to obtain the high-frequency System
Clock from the PLL or Main Clock. The divisor
is (FCDIV + 1).
MODE The PLL MODE field specifies the operation
mode of the on-chip PLL. After reset the
MODE bits are initialized to 100b, so the PLL
is configured to generate a 48-MHz clock.
This register must not be modified when the
System Clock is derived from the PLL Clock.
The System Clock must be derived from the
low-frequency oscillator clock while the
MODE field is modified.
11.9.3 Low Frequency Clock Prescaler Register
(PRSSC)
The PRSSC register is a byte-wide read/write register that
holds the clock divisor used to generate the Slow Clock from
the Main Clock. The register is initialized to B6h at reset.
SCDIV The Slow Clock Divisor field specifies a divi-
sor to be used when generating the Slow
Clock from the Main Clock. The Main Clock is
divided by a value of (2 × (SCDIV + 1)) to ob-
tain the Slow Clock. At reset, the SCDIV reg-
ister is initialized to B6h, which generates a
Slow Clock rate of 32786.89 Hz. This is about
0.5% faster than a Slow Clock generated from
an external 32768 Hz crystal network.
11.9.4 Auxiliary Clock Prescaler Register (PRSAC)
The PRSAC register is a byte-wide read/write register that
holds the clock divisor values for prescalers used to gener-
ate the two auxiliary clocks from the Main Clock. The regis-
ter is initialized to FFh at reset.
ACDIV1 The Auxiliary Clock Divisor 1 field specifies
the divisor to be used for generating Auxiliary
Clock 1 from the Main Clock. The Main Clock
is divided by a value of (ACDIV1 + 1).
ACDIV2 The Auxiliary Clock Divisor 2 field specifies
the divisor to be used for generating Auxiliary
Clock 2 from the Main Clock. The Main Clock
is divided by a value of (ACDIV2 + 1).
7 6 4 3 0
Res MODE FCDIV
MODE2:0
Output
Frequency
(from 12 MHz
input clock)
Description
000 Reserved Reserved
001 Reserved Reserved
010 Reserved Reserved
011 36 MHz 3× Mode
100 48 MHz 4× Mode
101 60 MHz 5× Mode
110 Reserved Reserved
111 Reserved Reserved
7 0
SCDIV
7 4 3 0
ACDIV2 ACDIV2