SPEAR600 datasheet(63/97 Pages) STMICROELECTRONICS

63 / 97 page

SPEAr600

Timing characteristics

Doc ID 16259 Rev 3

63/97

data are stable before the arrival of the DQS. To have a positive quantity the delay obtained

by the DQ (maximum delay or last variation) must be less than one obtained by the DQS

(minimum delay).

So:

t4MIN = DQS (delay)MIN - DQ (delay)MAX = (t1MIN + T ± one DLL element

(a) + t2

MIN) - (T*3/4

± one DLL element(a) + t3MAX) = t1MIN + T/4 + t2MIN ± one DLL element

(a) - t3

MAX

t5 can be expressed in a similar way, and can be defined as the tHOLD of the data:

t5MIN = DQ (delay)MIN - DQS (delay)MAX = (T/2 + T*3/4 ± one DLL element

(a) + t3

MIN) -

(t1MAX + T ± one DLL element

(a) + t2

MAX) =

= T/4 + t3MIN - t2MAX - t1MAX ± one DLL element

(a)

Note:

DQS (delay) is the combination of delays experienced by the DQS (data strobe) signal, DQ

(delay) is the combination of delays experienced by the DQ (data) signal (both until the

capture performed by the controller).

6.1.3

DDR2 command timings

Figure 8.

DDR2 command waveforms

Figure 9.

DDR2 command path

For the command and control timings, we have to consider that the commands are launched

on the negative edge of the clock and are captured on the next positive edge of the clock.

The value “one DLL element” stands for the DLL accuracy, so we put ± one DLL element in the formulas. One

DLL element = 15 ps in best case and 85 ps in worst case.

CLK

ADDRESS, STROBEs,

and CONTROL LINES

SET

CLR

CLK

ADDRESS, STROBEs,

and CONTROL LINES

ADDRESS, STROBEs,

and CONTROL LINES

CLK

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