
QuadFALCTM
PEF 22554 E
T1/J1 Registers
Data Sheet
544
Rev. 1.2, 2006-01-26
Global Clock Mode Register 6
Note: Write operations to GCM5 and GCM6 initiate a PLL reset if the asynchronous interface is selected (IM(1:0)
= 0xB) and if the “flexible master clocking mode” is selected (GCM2.VFREQ_EN = 1B), see Chapter 3.4.6.1. Flexible Clock Mode Settings
If “flexible master clock mode” is used (VFREQ_EN = 1B), the according register settings can be calculated as
follows (a windows-based program for automatic calculation is available, see Chapter 13.3. 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. 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 + 100 ppm) = 24.7064 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 0B.
5. To bring the “characteristic T1 frequency”
f
outT1 exact to 16 x fDATA_T1 = 24.70400 MHz a correction value
PHD_T1 is necessary:
PHD_T1 = round (12288 x { [PHSN_T1 + (PHSX_T1 / 6)] - [
f
PLL /16 x fDATA_T1] }) .
GCM6_T
Offset
Reset Value
Global Clock Mode Register 6
0097H
00H
Field
Bits
Type
Description
PLL_N
5:0
rw
PLL Dividing Factor N
For details see calculation formulas below.
000001B 1
..........B ,
111111B 63