K4Y50164UC Datasheet, PDF (23/76 Pages) Samsung semiconductor – 512Mbit XDR TM DRAM(C-die)

K4Y50164UC
K4Y50084UC
K4Y50044UC
K4Y50024UC
XDR^TM DRAM
7.5 Dynamic Request Scheduling
Delay fields are present in the ROWA, COL, and ROWP packet. They permit the associated command to optionally wait for a time of one
(or more) t_CYCLE before taking effect. This allows a memory controller more scheduling flexibility when issuing request packets. Figure8
illustrates the use of the delay fields.
In the first timing diagram, a ROWA packet with an ACT command is present at cycle T₀. The DELA field is set to “1”. This request
packet will be equivalent to a ROWA packet with an ACT command at cycle T₁ with the DELA field is set to “0”. This equivalence should
be used when analyzing request packet interactions.
In the second timing diagram, a COL packet with a RD command is present at cycle T₀. The DELC field is set to “1”. This request packet
will be equivalent to a COL packet with an RD command at cycle T₁ with the DELC field is set to “0”. This equivalence should be used
when analyzing request packet interactions.
In a similar fashion, a COL packet with a WR command is present at cycle T₁₂. The DELC field is set to”1”. This request packet will be
equivalent to a COL packet with a WR command at cycle T₁₃ with the DELC field is set to “0”. This equivalence should be used when
analyzing request packet interactions.
In the COL packet with a RD command example, the read data delay, t_CAC is measured between the Q read data packet and the virtual
COL packet at cycle T₁.
Likewise, for the example with the COL packet with a WR command, the write data delay, t_CWD is measured between the D write data
packet and the virtual COL packet at cycle T₁₃.
In the third timing diagram, a ROWP packet with a PRE command is present at cycle T₀. The DEL field(POP[1:0]) is set to “11”. This
request packet will be equivalent to a ROWP packet with a PRE command at cycle T₁ with the DEL field is set to “10”, it will be equiva-
lent to a ROWP packet with a PRE commmand at cycle T₂ with the DEL field is set to “01”, and it will be equivalent to a ROWP packet
with a PRE command at cycle T₃ with the DEL field is set to “00”. This equivalence should be used when analyzing request packet inter-
actions.
In the fourth timing diagram, a ROWP packet with a REFP command is present at cycle T₀. The DEL field(RA[7:6] ) is set to “11”. This
request packet will be equivalent to a ROWP packet with a REFP command at cycle T₁ with the DEL field is set to “10”, it will be equiva-
lent to a ROWP packet with a REFP command at cycle T₂ with the DEL field is set to “01”, and it will be equivalent to a ROWP packet
with a REFP command at cycle T₃ with the DEL field is set to “00”. This equivalence should be used when analyzing request packet
interactions.
The two examples for the REFA and REFI commands are identical to the example just described for the REFP command.
The ROWP packet allows two independent operations to be specified. A PRE precharge command uses the POP and BP fields, and the
REFP, REFA, or REFI commands use the ROP and RA fields. Both operations have an optional delay field(the POP field for the PRE
command and the RA field with the REFP, REFA, or REFI commands). The two delay mechanisms are independent of one another. The
POP field does not affect the timing of the REFP, REFA, or REFI commands, and the RA field does not affect the timing of the PRE
command.
When the interactions of a ROWP packet are analyzed, it must be remembered that there are two independent commands specified,
both of which may affect how soon the next request packet can be issued. The constraints from both commands in a ROWP packet must
be considered, and the one that requires the longer time interval to the next request packet must be used by the memory controller.
Furthermore, the two commands within a ROWP packet may not reference the same bank in the BP and RA fields.
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Rev. 1.1 August 2006