Motorola ColdFire MCF5281 User Manual
Page 179
Clock Module
Freescale Semiconductor
9-9
Table 9-5. SYNSR Field Descriptions
Bit(s)
Name
Description
7
PLLMODE
Clock mode bit. The PLLMODE bit is configured at reset and reflects the clock mode
as shown in
.
1 PLL clock mode
0 External clock mode
6
PLLSEL
PLL select. Configured at reset and reflects the PLL mode as shown in
1 Normal PLL mode
0 1:1 PLL mode
5
PLLREF
PLL reference. Configured at reset and reflects the PLL reference source in normal
PLL mode as shown in
1 Crystal clock reference
0 External clock reference
4
LOCKS
Sticky indication of PLL lock status.
1 No unintentional PLL loss of lock since last system reset or MFD change
0 PLL loss of lock since last system reset or MFD change or currently not locked due
to exit from STOP with FWKUP set
The lock detect function sets the LOCKS bit when the PLL achieves lock after:
• A system reset
• A write to SYNCR that changes the MFD[2:0] bits
When the PLL loses lock, LOCKS is cleared. When the PLL relocks, LOCKS remains
cleared until one of the two listed events occurs.
In stop mode, if the PLL is intentionally disabled, then the LOCKS bit reflects the value
prior to entering stop mode. However, if FWKUP is set, then LOCKS is cleared until
the PLL regains lock. Once lock is regained, the LOCKS bit reflects the value prior to
entering stop mode. Furthermore, reading the LOCKS bit at the same time that the
PLL loses lock does not return the current loss of lock condition.
In external clock mode, LOCKS remains cleared after reset. In normal PLL mode and
1:1 PLL mode, LOCKS is set after reset.
3
LOCK
Set when the PLL is locked. PLL lock occurs when the synthesized frequency is within
approximately 0.75 percent of the programmed frequency. The PLL loses lock when a
frequency deviation of greater than approximately 1.5 percent occurs. Reading the
LOCK flag at the same time that the PLL loses lock or acquires lock does not return
the current condition of the PLL. The power-on reset circuit uses the LOCK bit as a
condition for releasing reset.
If operating in external clock mode, LOCK remains cleared after reset.
1 PLL locked
0 PLL not locked
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3