HYB18H512321AF
512-Mbit GDDR3
Functional Description
4.10
Auto Refresh Command (AREF)
AREF is used to do a refresh cycle on one row in each
bank. The addresses are generated by an internal
refresh controller; external address pins are “DON’T
CARE”. All banks must be idle before the AREF
command can be applied. The delay between the
AREF command and the next ACT or subsequent
AREF must be at least tRFC(min). The refresh period
starts when the AREF command is entered and ends
tRFC later at which time all banks will be in the idle state.
CLK#
CLK
CKE
CS#
Within a period of tREF the whole memory has to be
RAS#
CAS#
refreshed. The average periodic interval time from
AREF to AREF is then tREFI
.
To improve efficiency bursts of AREF commands can
be used. Such bursts may consist of maximum 8 AREF
commands. tRFC(min) is the minimum required time
between two AREF commands inside of one AREF
burst. According to the number of AREF commands in
one burst the average required time from one AREF
burst to the next can be increased. Example: If the
AREF bursts consists of 8 AREF commands, the
average time from one AREF burst to the next is 8*
WE#
A0-A11
BA: Bank Address
Don't Care
BA0-BA2
tREFI
.
Figure 52 Auto Refresh Command
The AREF command generates an update of the OCD
output impedance and of the addresses, commands
and DQ terminations. The timing parameter tKO (see
Chapter 4.2.2 must be met.
CLK#
CLK
Command
CKE
PRE
ARF
NOP
A.C.
NOP
ARF
NOP
tRP
tRFC
A.C.: AREF or ACT Command
ARF: Auto Refresh
tREFI
Don't Care
Figure 53 Auto Refresh Cycle
Data Sheet
70
Rev. 1.73, 2005-08
05122004-B1L1-JEN8
QIMONDA [ QIMONDA AG ]
