CS2000-OTP

20

DS758PP1

5.7

Mode Pin Functionality

5.7.1

M1 and M0 Mode Pin Functionality

M[1:0] determine the functional mode of the device and select both the default User Defined Ratio and

the set of modal parameters. The modal parameters are RModSel[1:0], AuxOutSrc[1:0], AutoRMod, Lock-

Clk[1:0], and FracNSrc. By modifying one or more of the modal parameters between the 4 sets, different

functional configurations can be achieved. However, global parameters are fixed and the same value will

be applied to each functional configuration. Figure 16 on page 23 provides a summary of all parameters

used by the device.

5.7.2

M2 Mode Pin Functionality

M2 usage is mapped to one of the optional special functions via the M2Config[2:0] global parameter. De-

pending on what M2 is mapped to, it will either act as an output enable/disable pin or override certain mod-

al parameters. Figure 15 summarizes the available options and the following sections will describe each

option in more detail.

Figure 15. M2 Mapping Options

5.7.2.1

M2 Configured as Output Disable

If M2Config[2:0] is set to either ‘000’, ‘001’, or ‘010’, M2 becomes an output disable pin for one or

both output pins. If M2 is driven ‘low’, the corresponding output(s) will be enabled, if M2 is driven

‘high’, the corresponding output(s) will be disabled.

5.7.2.2

M2 Configured as R-Mod Enable

If M2Config[2:0] is set to ‘011’, M2 becomes the R-Mod enable pin. It should be noted that M2 is

the only way to enable R-Mod. Even though the RModSel[1:0] modal parameter can be set arbi-

trarily for each configuration set, it will not take effect unless enabled via M2. If M2 is driven ‘low’,

R-Mod will be disabled, if M2 is driven ‘high’ R-Mod will be enabled.

M2 pin

Disable CLK_OUT and AUX_OUT pins

Disable AUX_OUT pin

Disable CLK_OUT pin

RModSel[1:0] Modal Parameter Enable

Force AuxOutSel[1:0] = 10 (PLL Clock Out)

AutoRMod Modal Parameter Override

Force Manual Fractional N Source Selection

M2Config[2:0] global parameter

000

001

010

011

100

101

110

111

FracNSrc Modal Parameter Override