Clocks and Power Control
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
8-13
The clocks GCLK1_50 and GCLK2_50 frequency is:
shows the timing of USIU clocks when DFNH = 1 or DFNL = 0.
Figure 8-7. Clocks Timing For DFNH = 1 (or DFNL = 0)
8.5.2
Clock Out (CLKOUT)
CLKOUT has the same frequency as the general system clock (GCLK2_50). Unlike the main system clock
GCLK1/GCLK2 however, CLKOUT (and GCLK2_50) represents the external bus clock, and thus will be
one-half of the main system clock if the external bus is running at half speed (EBDF = 0b01). The
CLKOUT frequency (system frequency) defaults to VCO/2. CLKOUT can drive full, half, or quarter
strength; it can also be disabled. The drive strength is controlled in the system clock and reset-control
register (SCCR) by the COM[0:1] and CQDS bits. (See
Section 8.11.1, “System Clock Control Register
). Disabling or decreasing the strength of CLKOUT can reduce power consumption, noise, and
electromagnetic interference on the printed circuit board.
When the PLL is acquiring lock, the CLKOUT signal is disabled and remains in the low state (provided
that BUCS = 0).
FREQ
50
FREQsysmax
2
DFNH
(
)
or 2
DFNL
1
+
(
)
-------------------------------------------------------------------
x
1
EBDF
1
+
--------------------------
=
GCLK1
GCLK2
GCLK1_50
GCLK2_50
CLKOUT
GCLK1_50
GCLK2_50
(EBDF = 00)
(EBDF = 00)
(EBDF = 01)
(EBDF = 01)
CLKOUT
(EBDF = 00)
(EBDF = 01)
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...