
Data Sheet
131
Rev. 1.0, 2005-06-02
OctalLIUTM
PEF 22508 E
Register DescriptionGlobal Clock Mode Register 6
Global Clock Mode Register 6
Flexible Clock Mode Settings
If “flexible master clock mode” is used (VFREQ_EN = 1), the according register settings can be calculated as
follows (a windows-based program for automatic calculation is available, see Chapter 8.3. For some of the
standard frequencies see the table below.
1. The master clock MCLK must be in the following frequency range:
1.02 MHz
≤ f
MCLK ≤ 20 MHz
2. Generally the PLL of the master clocking unit includes an input divider with a dividing factor PLL_M +1 and a
feedback divider with a dividing factor 4 x (PLL_N +1). So it generates a clock
f
PLL of about
f
PLL = fMCLK x 4 x (PLL_N +1) / (PLL_M +1) .
3. The selection of PLL_N and PLL_M must be done in the following way:
The PLL frequency
f
PLL must be in the following range:
200 MHz
≤ f
PLL ≤ 300 MHz .
The combinations of the values PLL_M and PLL_M must fulfill the equations:
2 MHz
≤ f
MCLK / (PLL_M +1) ≤ 6 MHz , if PLL_N is in the range 25 to 63.
5 MHz
≤ f
MCLK / (PLL_M +1) ≤ 15 MHz , if PLL_N is in the range 1 to 24.
4. In E1 mode, the selection of PHSN_E1 and PHSX_E1 must be done in such a manner that the frequency for
the receiver
f
RX_E1 has nearly the value 16 x fDATA_E1 x (1 + 100ppm) = 32.7713 MHz:
f
RX_E1 = fPLL / {PHSN_E1 + (PHSX_E1 / 6)} .
In T1/J1 mode, the selection of PHSN_T1 and PHSX_T1 must be done in such a manner that the frequency for
the receiver
f
RX_T1 has nearly the value 16 x fDATA_T1 x (1 + 100ppm) = 24.706 MHz:
f
RX_T1 = fPLL / {PHSN_T1 + (PHSX_T1 / 6)} .
GCM2.PHSDEM, GCM2.PHSDIR, GCM2.PHSDS, PC5.PHDSX and PC5.PHDSR must be left to 0
5. To bring the “characteristic E1 frequency”
f
outE1 exact to 16 x fDATA_E1 = 32.7680 MHz a correction value PHD_E1
is necessary:
PHD_E1 = round (12288 x { [PHSN_E1 + (PHSX_E1 / 6)] - [
f
pll / (16 x fDATA_E1)] }) .
GCM6
Offset
Reset Value
Global Clock Mode Register 6
0097H
00H
Field
Bits
Type
Description
PLL_N
4:0
rw
PLL Dividing Factor N
For details see calculation formulas below and Table 45.
000001B, 1
...........B,
111111B, 63