MPC5200 datasheet(24/80 Pages) FREESCALE

24 / 80 page

MPC5200 Data Sheet, Rev. 4

Electrical and Thermal Characteristics

Freescale Semiconductor

Figure 8. Read Data sample window depend on the number of Tap delay

The position of the tdata_valid window is depend on the clock / data flight time on the board. The MDQS

signal indicate if the read data are valid. If the controller is not able to detect a valid MDQS signal on the

sample time (sample position A) then the controller will look for valid MDQS / data on the next edge of

the MEM_CLK signal (sample position B). Depend on the board travel time, different working tap delay

configurations are possible. For a fast connection the data will be sampled with the next edge of

MEM_CLK, this shows Figure 8, sample position A. With a longer connection maybe two sample

positions are possible. Figure 8 shows a example with two working sample position (A and B). With a

bigger board delay only sample position B will be possible.

The equation below shows how to calculate the upper and lower limit. The right Tap delay number is

selected, when the possible max and min sample timing is within the memory data valid window.

•tdata_sample_max = max((1.55 + TapNum * 0.095), (1.74 + TapNum * 0.045))

•tdata_sample_min = min((1.55 + TapNum * 0.095), (1.74 + TapNum * 0.045))

delay [ns]

1.55

4.59

Possible sample

time over PVT for one

Memory Data valid window

selected Tap delay

Tap delay number

8.34

Working Tap Delay range

for sample position A

Working Tap Delay range

for sample position B

tdata_valid_min

tdata_valid_max

tdata_sample_min

selected Tap delay

MPC5200 датащи(PDF) 24 Page - Freescale Semiconductor, Inc