MSC8151 Datasheet, PDF (37/68 Pages) Freescale Semiconductor, Inc – Single-Core Digital Signal Processor

2.6 AC Timing Characteristics
This section describes the AC timing characteristics for the MSC8151.
Electrical Characteristics
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 V_DDDDR (typ) = 1.8 V.
Table 18. DDR2 SDRAM Input AC Timing Specifications for 1.8 V Interface
Parameter
Symbol
Min
Max
Unit
AC input low voltage
V_IL
AC input high voltage
V_IH
Note: At recommended operating conditions with V_DDDDR of 1.8 ± 5%.
—
MV_REF – 0.20
V
MV_REF + 0.20
—
V
Table 19 provides the input AC timing specifications for the DDR SDRAM when V_DDDDR (typ) = 1.5 V.
Table 19. DDR3 SDRAM Input AC Timing Specifications for 1.5 V Interface
Parameter
Symbol
Min
Max
Unit
AC input low voltage
V_IL
AC input high voltage
V_IH
Note: At recommended operating conditions with V_DDDDR of 1.5 ± 5%.
—
MV_REF – 0.175
V
MV_REF + 0.175
—
V
Table 20 provides the input AC timing specifications for the DDR SDRAM interface.
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
t_CISKEW
–200
–240
1, 2
200
ps
240
ps
Tolerated Skew for MDQS—MDQ/MECC/MDM
• 800 MHz data rate
• 667 MHz data rate
t_DISKEW
–425
–510
2, 3
425
ps
510
ps
Notes: 1. t_CISKEW 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.
2. At recommended operating conditions with V_DDDDR (1.8 V or 1.5 V) ± 5%
3. The amount of skew that can be tolerated from MDQS to a corresponding MDQ signal is called t_DISKEW.This can be
determined by the following equation: t_DISKEW = ±(T ÷ 4 – abs(t_CISKEW)) where T is the clock period and abs(t_CISKEW) is the
absolute value of t_CISKEW.
MSC8151 Single-Core Digital Signal Processor Data Sheet, Rev. 1
Freescale Semiconductor
37