SPEAR600 datasheet(64/97 Pages) STMICROELECTRONICS

64 / 97 page

Timing characteristics

SPEAr600

64/97

Doc ID 16259 Rev 3

Therefore, we have to add the value T to the clock path and the value T/2 to the command

path.

The waveform shown in Figure 8 refers to the pad or memory side, so the CLK edges are

centered on the command valid window. In this case, we consider the minimum values for t4

and t5 in order to obtain the minimum command valid window. We can consider t4 as the

tSETUP of the commands that can be defined as the time range where the commands are

stable before the arrival of the clock. To have a positive quantity the delay obtained by the

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

clock (minimum delay).

So:

t4MIN = CLK (delay) MIN - CMD (delay) MAX =(T + t3MIN) - (T/2 + t2MAX) = T/2 - t2MAX + t3MIN

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

t5MIN = CMD (delay)MIN - CLK (delay)MAX = (T + T/2 + t2MIN) - (T + t3MAX) = T/2 - t3MAX

+t2MIN

Note:

CLK(delay) is the combination of delays experienced by the CLK signal, CMD(delay) is the

combination of delays experienced by the command/ctrl/address signal (both until the

capture performed by the memory).

Table 35 shows the internal chip timing without the contribution of the pads.

Table 35.

DDR2 command timings without pad delay

Period (T)

Frequency

t4MIN

t5MIN

3 ns

333 MHz

977 ps

1.33 ns

3.75 ns

266 MHz

1.35 ns

1.71 ns

5 ns

200 MHz

1.98 ns

2.33 ns

6 ns

166 MHz

2.49 ns

2.84 ns

7.5 ns

133 MHz

3.23 ns

3.59 ns

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