
UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
47 of 268
NXP Semiconductors
UM10413
MPT612 User manual
10.8.5 PLL interrupt
Bit PLOCK in register PLLSTAT is connected to the interrupt controller. This allows for
software to turn on the PLL and continue with other functions without having to wait for the
PLL to achieve lock. When the interrupt occurs (PLOCK = 1), the PLL can be connected,
and the interrupt disabled. For details on how to enable and disable the PLL interrupt, see
Section 9.4.4 “Interrupt enable register (VICIntEnable - 0xFFFF F010)” on page 23
and
Section 9.4.5 “Interrupt enable clear register (VICIntEnClear - 0xFFFF F014)” on page 23
.
10.8.6 PLL modes
The combinations of PLLE and PLLC are shown in
10.8.7 PLL Feed register (PLLFEED - 0xE01F C08C)
In order for changes to registers PLLCON and PLLCFG to take effect, write a correct feed
sequence to register PLLFEED. The feed sequence is:
1. Write the value 0xAA to PLLFEED.
2. Write the value 0x55 to PLLFEED.
The two writes must be in the correct sequence, and must be consecutive APB bus
cycles. The latter requirement implies that interrupts must be disabled for the duration of
the PLL feed operation. If either of the feed values is incorrect, or one of the previously
mentioned conditions is not met, any changes to register PLLCON or PLLCFG are not
effective.
9
PLLC
read-back for bit PLL Connect. When PLLC and PLLE are both
logic 1, the PLL is connected as the clock source for the MPT612.
When either PLLC or PLLE is logic 0, the PLL is bypassed and the
oscillator clock is used directly by the MPT612. This bit is
automatically cleared when Power-down mode is activated.
0
10
PLOCK
reflects the PLL Lock status. When logic 0, the PLL is not locked.
When logic 1, the PLL is locked onto the requested frequency.
0
15:11
-
reserved, user software must not write logic 1s to reserved bits; the
value read from a reserved bit is not defined
n/a
Table 47.
PLL status register (PLLSTAT - address 0xE01F C088) bit description
…continued
Bit
Symbol
Description
Reset
value
Table 48.
PLL Control bit combinations
PLLC
PLLE
PLL Function
0
0
PLL is off and disconnected. CCLK equals the unmodified clock input.
0
1
PLL is active, but not yet connected. PLL can be connected after PLOCK is
asserted.
1
0
same as 00 combination. Prevents possibility of PLL being connected without
also being enabled.
1
1
PLL is active and connected. CCLK/system clock is sourced from the PLL.