Internet Data Sheet
Rev. 1.1, 2007-01 13
03292006-SR4U-HULB
HYB25DC256163CE
256-Mbit Double-Data-Rate SGRAM
TABLE 10
Truth Table 3: Current State Bank n - Command to Bank n (same bank)
Current State CS RAS CAS WE Command Action Note
Any H X X X Deselect NOP. Continue previous operation. 1)2)3)4)5)6)
1) This table applies when CKE n-1 was HIGH and CKE n is HIGH (see Table 9 and after tXSNR/tXSRD has been met (if the previous state was
self refresh).
2) This table is bank-specific, except where noted, i.e., the current state is for a specific bank and the commands shown are those allowed
to be issued to that bank when in that state. Exceptions are covered in the notes below.
3) Current state definitions:
Idle: The bank has been precharged, and tRP has been met.
Row Active: A row in the bank has been activated, and tRCD has been met. No data bursts/accesses and no register accesses are in
progress.
Read: A Read burst has been initiated, with Auto Precharge disabled, and has not yet terminated or been terminated.
Write: A Write burst has been initiated, with Auto Precharge disabled, and has not yet terminated or been terminated.
4) The following states must not be interrupted by a command issued to the same bank.
Precharging: Starts with registration of a Precharge command and ends when tRP is met. Once tRP is met, the bank is in the idle state.
Row Activating: Starts with registration of an Active command and ends when tRCD is met. Once tRCD is met, the bank is in the “row active”
state.
Read w/Auto Precharge Enabled: Starts with registration of a Read command with Auto Precharge enabled and ends when tRP has been
met. Once tRP is met, the bank is in the idle state.
Write w/Auto Precharge Enabled: Starts with registration of a Write command with Auto Precharge enabled and ends when tRP has been
met. Once tRP is met, the bank is in the idle state. Deselect or NOP commands, or allowable commands to the other bank should be issued
on any clock edge occurring during these states. Allowable commands to the other bank are determined by its current state and according
to Table 11.
5) The following states must not be interrupted by any executable command; Deselect or NOP commands must be applied on each positive
clock edge during these states.
Refreshing: Starts with registration of an Auto Refresh command and ends when tRFC is met. Once tRFC is met, the DDR SGRAM is in the
“all banks idle” state.
Accessing Mode Register: Starts with registration of a Mode Register Set command and ends when tMRD has been met. Once tMRD is met,
the DDR SGRAM is in the “all banks idle” state.
Precharging All: Starts with registration of a Precharge All command and ends when tRP is met. Once tRP is met, all banks is in the idle state.
6) All states and sequences not shown are illegal or reserved.
L H H H No Operation NOP. Continue previous operation. 1) to 6)
Idle L L H H Active Select and activate row 1) to 6)
L L L H AUTO REFRESH – 1) to7)
7) Not bank-specific; requires that all banks are idle.
LLLLMODE REGISTER
SET
–1) to 7)
Row Active L H L H Read Select column and start Read burst 1) to 6),8)
8) Reads or Writes listed in the Command/Action column include Reads or Writes with Auto Precharge enabled and Reads or Writes with
Auto Precharge disabled.
L H L L Write Select column and start Write burst 1) to 6),8)
L L H L Precharge Deactivate row in bank(s) 1) to 6),9)
9) May or may not be bank-specific; if all/any banks are to be precharged, all/any must be in a valid state for precharging.
Read (Auto
Precharge
Disabled)
L H L H Read Select column and start new Read burst 1) to 6),8)
L L H L Precharge Truncate Read burst, start Precharge 1) to 6),9)
L H H L BURST
TERMINATE
BURST TERMINATE 1) to 6),10)
Write (Auto
Precharge
Disabled)
L H L H Read Select column and start Read burst 1) to 6), 8),11)
L H L L Write Select column and start Write burst 1) to 6),8)
L L H L Precharge Truncate Write burst, start Precharge 1) to 6),9),11)