MSC8252 datasheet(36/68 Pages) FREESCALE

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MSC8252 Dual-Core Digital Signal Processor Data Sheet, Rev. 3

Electrical Characteristics

Freescale Semiconductor

2.6

AC Timing Characteristics

This section describes the AC timing characteristics for the MSC8252.

2.6.1

DDR SDRAM AC Timing Specifications

This section describes the AC electrical characteristics for the DDR SDRAM interface.

2.6.1.1

DDR SDRAM Input AC Timing Specifications

Table 18 provides the input AC timing specifications for the DDR SDRAM when VDDDDR (typ) = 1.8 V.

Table 19 provides the input AC timing specifications for the DDR SDRAM when VDDDDR (typ) = 1.5 V.

Table 20 provides the input AC timing specifications for the DDR SDRAM interface.

Table 18. DDR2 SDRAM Input AC Timing Specifications for 1.8 V Interface

Parameter

Symbol

Min

Max

Unit

AC input low voltage

VIL

—MVREF – 0.20

AC input high voltage

VIH

MVREF + 0.20

—

Note:

At recommended operating conditions with VDDDDR of 1.8 ± 5%.

Table 19. DDR3 SDRAM Input AC Timing Specifications for 1.5 V Interface

Parameter

Symbol

Min

Max

Unit

AC input low voltage

VIL

—MVREF – 0.175

AC input high voltage

VIH

MVREF + 0.175

—

Note:

At recommended operating conditions with VDDDDR of 1.5 ± 5%.

Table 20. DDR SDRAM Input AC Timing Specifications

Parameter

Symbol

Min

Max

Unit

Notes

Controller Skew for MDQS—MDQ/MECC/MDM

• 800 MHz data rate

• 667 MHz data rate

tCISKEW

–200

–240

200

240

1, 2

Tolerated Skew for MDQS—MDQ/MECC/MDM

• 800 MHz data rate

• 667 MHz data rate

tDISKEW

–425

–510

425

510

2, 3

Notes:

tCISKEW represents the total amount of skew consumed by the controller between MDQS[n] and any corresponding bit that is

captured with MDQS[n]. Subtract this value from the total timing budget.

At recommended operating conditions with VDDDDR (1.8 V or 1.5 V) ± 5%

The amount of skew that can be tolerated from MDQS to a corresponding MDQ signal is called tDISKEW.This can be

determined by the following equation: tDISKEW =±(T ÷ 4 – abs(tCISKEW)) where T is the clock period and abs(tCISKEW) is the

absolute value of tCISKEW.

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