W641GG2JB Datasheet, PDF (86/109 Pages) Winbond – 1-Gbit GDDR3 Graphics SDRAM

W641GG2JB
1-Gbit GDDR3 Graphics SDRAM
6.19 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 within the ranks 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 t_RFC(min). The refresh period starts when the
AREF command is entered and ends t_RFC later at which time all banks will be in the idle state.
Within a period of t_REF the whole memory has to be refreshed. The average periodic interval time from AREF to AREF is then t_REFI.
To improve efficiency bursts of AREF commands can be used. Such bursts may consist of maximum 8 AREF commands. t_RFC(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 * t_REFI.
The AREF command generates an update of the OCD output impedance and of the addresses, commands and DQ terminations.
The timing parameter t_KO .
AREF affects one rank, only. Therefore, accesses to the other rank in the 2-CS-mode are allowed after t_KO has expired.
6.19.1 Auto Refresh Command
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Publication Release Date: Apr, 22, 2011
Revision A01-002