Clock Generation and Reset Control Registers
15-72
Table 15–25. DPLL Control Register (CTL_REG)
Bit
Name
Description
Type
Reset
Value
15–14
RESERVED
This bit is reserved and set to 0.
13
IOB
Initialize on break. When high, DPLL switches to bypass
mode and starts a new locking sequence if DPLL core
indicates that it lost lock. When set low, DPLL continues
to output synthesized clock even if core indicates it has
lost lock, but BREAKLN is active low. The power-on
value is 1.
12
RESERVED
This bit is reserved and set to 0.
11–7
PLL_MULT(4–0)
The DPLL multiply value. The maximum clock out
frequency is 31*CLKREF.
6–5
PLL_DIV(1:0)
The DPLL divide value.
PLL_DIV(1:0) = 00: CLKOUT = CLKREF
01: CLKOUT = CLKREF/2
10: CLKOUT = CLKREF/3
11: CLKOUT = CLKREF/4
The minimum CLKOUT frequency is 0.25 * CLKREF.
When PLL_MULT(4:0) is equal to 0 or 1, CLKOUT is not
synthesized by DPLL but by simply a divided down
version of CLKREF. Affects lock mode only.
4
PLL_ENABLE
Setting PLL_ENABLE bit to 1 requests DPLL to enter
LOCK mode. It enters LOCK mode only after it has
synthesized desired frequency. Clearing bit to 0 causes
DPLL to switch back to bypass mode.
3–2
BYPASS_DIV(1:0)
Determines clkout frequency when in BYPASS mode.
BYPASS_DIV(1:0) = 00: CLKOUT = CLKREF
01: CLKOUT = CLKREF/2
1X: CLKOUT = CLKREF/4
1
BREAKLN
When BREAKLN = 0, DPLL has broken lock for some
unknown reason. If and when lock condition is restored
or a write to control register occurs, BREAKLN returns to
1.
0
LOCK
When LOCK = 1, DPLL is in lock mode and clkout is
desired synthesized clock frequency. When LOCK = 0,
DPLL is in bypass mode and clkout contains a divided
down output clock.
If PLL_MULT = 0 or 1, oscillators in DPLL_core are not
activated and duty cycle is not ensured.