Rev. 1.4 / July 2006

32

HY5PS12821(L)F

HY5PS121621(L)F

10. The maximum limit for this parameter is not a device limit. The device will operate with a greater value for this

parameter, but system performance (bus turnaround) will degrade accordingly.

11. MIN ( t CL, t CH) refers to the smaller of the actual clock low time and the actual clock high time as provided to the

device (i.e. this value can be greater than the minimum specification limits for t CL and t CH). For example, t CL and t

CH are = 50% of the period, less the half period jitter ( t JIT(HP)) of the clock source, and less the half period jitter due

to crosstalk ( t JIT(crosstalk)) into the clock traces.

12. t QH = t HP – t QHS, where:

tHP = minimum half clock period for any given cycle and is defined by clock high or clock low ( tCH, tCL).

tQHS accounts for:

1) The pulse duration distortion of on-chip clock circuits; and

2) The worst case push-out of DQS on one transition followed by the worst case pull-in of DQ on the next transi-

tion, both of which are, separately, due to data pin skew and output pattern effects, and p-channel to n-channel varia-

tion of the output drivers.

13. tDQSQ: Consists of data pin skew and output pattern effects, and p-channel to n-channel variation of the output

drivers as well as output slew rate mismatch between DQS/ DQS and associated DQ in any given cycle.

14. t DAL = (nWR) + ( tRP/tCK):

For each of the terms above, if not already an integer, round to the next highest integer. tCK refers to the application

clock period. nWR refers to the t WR parameter stored in the MRS.

Example: For DDR533 at t CK = 3.75 ns with t WR programmed to 4 clocks. tDAL = 4 + (15 ns / 3.75 ns) clocks =4

+(4)clocks=8clocks.

15. The clock frequency is allowed to change during self–refresh mode or precharge power-down mode. In case of

clock frequency change during precharge power-down, a specific procedure is required as described in section 2.9.

16. ODT turn on time min is when the device leaves high impedance and ODT resistance begins to turn on.

ODT turn on time max is when the ODT resistance is fully on. Both are measured from tAOND.

17. ODT turn off time min is when the device starts to turn off ODT resistance.

ODT turn off time max is when the bus is in high impedance. Both are measured from tAOFD.

18. tHZ and tLZ transitions occur in the same access time as valid data transitions. Thesed parameters are

referenced to a specific voltage level which specifies when the device output is no longer driving(tHZ), or begins driving

(tLZ). Below figure shows a method to calculate the point when device is no longer driving (tHZ), or begins driving (tLZ)

by measuring the signal at two different voltages. The actual voltage measurement points are not critical as long as the

calculation is consistent.

19. tRPST end point and tRPRE begin point are not referenced to a specific voltage level but specify when the device

output is no longer driving (tRPST), or begins driving (tRPRE). Below figure shows a method to calculate these points

when the device is no longer driving (tRPST), or begins driving (tRPRE). Below Figure shows a method to calculate

different voltages. The actual voltage measurement points are not critical as long as the calculation is consistent.