m21262 Mindspeed Technologies, m21262 Datasheet - Page 12

• Manufacturer Part Number: m21262
• Description: Cdr/reclocker With 4 1 Input Multiplexer
• Manufacturer: Mindspeed Technologies

1.1.6
An external reference clock is applied to RefClk[P/N] to enable frequency acquisition in the Reclocker. PCML,
LVTTL, CMOS are examples of the wide variety of interfaces supported for the reference clock. The inputs contain
a DC-coupled 100 Ω differential termination between RefClkP and RefClkN along with a 100 k Ω pull-down on each
terminal to Vss. After this termination/pull-down block, the inputs are AC coupled internally. The common-mode
and allowable voltage swings are specified in
which may require external pull-ups, in the case of external AC coupling.
1.1.7
The M21262 is designed to be an extremely versatile device, with many user selectable options in the CDR/RCLK
and I/O to optimize performance. All of these options can be accessed and controlled through the serial interface.
The serial interface I/O pins and address pins are mapped to the multifunction pins MF [11:0]. A subset of the key
features for most applications, such as standard data rates, I/O levels, etc., can be selected through MF [11:0] in
the hardwired mode. The hardwired mode does not require the use of the serial interface. In this mode, upon power
up (auto reset on power up), the M21262 function is determined by the status of the hardwired pins. During
operation, the hardwired pins can change states, which would cause the device to follow with the appropriate
action. Another feature of the multifunction pins is to support JTAG testing of this device during PCB manufacturing.
The various control and test modes of this device are selected with three pins: CTRL_Mode [1:0], and xJTAG_En.
xJTAG_En = L overrides CTRL_Mode [1:0], and puts the device in JTAG test mode, while xJTAG_En = H allows
CTRL_Mode [1:0] to determine the M21262 control mode, as summarized in
Table 1-4.
21262-DSH-001-C
CTRL_Mode [1:0]
xJTAG_En
Pin
Mode Select Pins
Reclocker Reference Frequency
Multifunction Pins Overview
JTAG Test Mode
no impact
L
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Hardwired Mode
Table
11b
H
2-10. The RefClk common-mode must be above 250 mV,
MSPD 4-Wire Serial
®
00b
H
Table
1-4.
I
Functional Description
2
C-Compatible 2-Wire Serial
01b
H
4