VSC7440 datasheet(303/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

286

addition. The transmitted SYNC therefore has ORG_TIME=’close to departure time’, and CF=’minor

correction to that’.

REW: PDU.ORGTIME := (TOD_sec, TOD_nsec)

REW: Preamble := (CF, NSF)

DEV: CF += NSF@mac_Tx-ofs

3.29.6

Time of Day Generation

The DEVCPU has connection to four GPIOs to be used for 1588 synchronization shown in the following

illustration.

Figure 86 •

Timing Distribution

Each block using timing has a TimeOfDay instance included. These modules let time pass according to

an incoming delta request, instructing it to add the nominal clock period in nanoseconds (+0/+1/–1) for

each system clock cycle. This is controlled by a deltaT function in the DEVCPU, which can be configured

to do regular adjustments to the time by adding a single nanosecond more or less at specified intervals.

The absT function in the DEVCPU can set the full TOD time in the system. This is controlled by the

LoadStore controllers.

The DEVCPU includes five LoadStore controllers. All but the last one use a designated GPIO pin on the

GPIO interface. LoadStore controller 0 uses PTP_0 pin; LoadStore controller 1 uses PTP_1 pin, and so

forth. Before using the LoadStore controller, the VCore-III CPU must enable the overlaid functions for the

appropriate GPIO pins. For more information, see GPIO Overlaid Functions, page 352.

Each controller has CPU accessible registers with the full time of day set, and can be configured to load

these into the TimeOfDay instances, or to store the current values from them. The operation can be done

on a detected edge on the associated pin or immediately. The GPIO pin can also generate a clock with

DeltaT

gen

Adjuster

LoadStore Ctrl

GPIO

AbsT

gen

LoadStore Ctrl

load

TimeOfDay

o o o

store

Five controllers configured for:

- Load absolute time

- Load signed delta time

- Store absolute time

- Generate pulse or clock on pin

Load/store can be done on incoming edge

or immediately.

sec (48 bits)

nsec (30 bits)

nsf (32 bits)

Analyzer / Rewriter / Port Modules

(only NSF in port module)

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