ICS2572M ICST [Integrated Circuit Systems], ICS2572M Datasheet - Page 4

• Manufacturer Part Number: ICS2572M
• Description: User-Programmable Dual High-Performance Clock Generator
• Manufacturer: ICST [Integrated Circuit Systems]

ICS2572
Observe that the internal shift register is “clocked” by a tran-
sition of FS3 data from “0” to “1.” If an extended sequence of
register loading is to be performed (such as a power-on initiali-
zation sequence), note that it is not necessary to implement the
50 millisecond delay between them. Simply repeat the se-
quence above as many times as desired. Writes to the FS port
will not be treated as frequency select data until up to 50
milliseconds have transpired since the last write. Note that FS0
and FS1 inputs are “don’t care.”
Data Description
Location Bits (L0-L4)
The first five bits after the start bit control the frequency
location to be re-programmed according to this table. The
rightmost bit (the LSB) of the five shown in each selection of
the table is the first one sent.
Feedback Set Bits (N0-N7)
These bits control the feedback divider setting for the location
specified. The modulus of the feedback divider will be equal
to the value of these bits + 257. The least significant bit (N0)
is sent first.
Post-Divider Set Bits (D0-D1)
These bits control the post-divider setting for the location
specified according to this table. The least significant bit (D0)
is sent first.
Table 1 - Location Bit Programming
L[4-0]
01100
01101
01110
10010
10011
01111
VCLK Address 12
VCLK Address 13
VCLK Address 14
VCLK Address 15
MCLK Address 2
MCLK Address 3
LOCATION
E-98
Read/Write* Control Bit
When set to a “0,” the ICS2572 shift register will transfer its
contents to the selected memory register at the completion of
the programming sequence outlined above.
When this bit is a “1,” the selected memory location will be
transferred to the shift register to permit a subsequent readback
of data. No modification of device memory will be performed.
To readback any location of memory, perform a “dummy”
write of data (complete with start and stop bits) to that location
but set the R/W* control bit (make it “1”). At the end of the
sequence (i.e., after the stop bits have been “clocked”), “clock-
ing” of the FS3 input 11 more times will output the data bits
only in the same sequence as above on the FS0 pin.
EXTFREQ Input
The EXTFREQ input allows an externally generated frequency
to be routed to the VCLK output pin under device program-
ming control. If the EXTFREQ bit is set (logic “1”) at the
selected address location (VCLK addresses only), the fre-
quency applied to the EXTFREQ input will be routed to the
VCLK output.
Table 2 - Post-Divider Programming
D[1-0]
00
01
10
11
POST-DIVIDER
9
4
2
1