K4D551638F-LC40000 Samsung, K4D551638F-LC40000 Datasheet - Page 8

• Manufacturer Part Number: K4D551638F-LC40000
• Description: No Discount To Anyone!
• Manufacturer: Samsung

MODE REGISTER SET(MRS)
addressing mode, burst length, test mode, DLL reset and various vendor specific options to make DDR SDRAM useful for
variety of different applications. The default value of the mode register is not defined, therefore the mode register must be
written after EMRS setting for proper operation. The mode register is written by asserting low on CS, RAS, CAS and
WE(The DDR SDRAM should be in active mode with CKE already high prior to writing into the mode register). The state of
address pins A
Minimum two clock cycles are requested to complete the write operation in the mode register. The mode register contents
can be changed using the same command and clock cycle requirements during operation as long as all banks are in the
idle state. The mode register is divided into various fields depending on functionality. The burst length uses A
addressing mode uses A
used for DLL reset. A
for various burst length, addressing modes and CAS latencies.
K4D551638F-TC
* RFU(Reserved for future use)
RFU
BA
The mode register stores the data for controlling the various operating modes of DDR SDRAM. It programs CAS latency,
should stay "0" during MRS
cycle.
MRS Cycle
BA
Command
0
1
1
CK, CK
0
BA
0
0
*1 : MRS can be issued only at all banks precharge state.
*2 : Minimum
EMRS
A
MRS
0
n
DLL
A
~ A
~ A
12
A
0
1
8
12
0
7,
and BA
A
A
DLL Reset
NOP
8
11
3
, BA
, CAS latency(read latency from column address) uses A
RFU
t
Yes
No
RP
0
0
is required to issue MRS command.
0
A
, BA
and BA
10
Precharge
All Banks
1
in the same cycle as CS, RAS, CAS and WE going low is written in the mode register.
A
1
1
9
must be set to low for normal MRS operation. Refer to the table for specific codes
CAS Latency
Test Mode
A
0
0
0
0
1
1
1
1
A
0
1
6
DLL
7
NOP
A
8
A
0
0
1
1
0
0
1
1
2
5
Normal
TM
Test
t
mode
A
RP
7
A
0
1
0
1
0
1
0
1
NOP
4
- 8 -
A
Latency
3
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
6
CAS Latency
3
MRS
A
5
Burst Type
4
A
0
1
3
A
Burst Length
t
4
MRD
NOP
A
0
0
0
0
1
1
1
1
Sequential
Interleave
2
=2 t
5
BT
A
Type
CK
A
0
0
1
1
0
0
1
1
3
4
1
~ A
Command
256M GDDR SDRAM
Any
A
0
1
0
1
0
1
0
1
A
6
. A
0
2
Burst Length
6
7
Sequential
is used for test mode. A
Reserve
Reserve
Reserve
Reserve
Reserve
A
1
NOP
Rev 2.1 (Apr. 2005)
2
4
8
Burst Type
7
A
0
NOP
Interleave
Reserve
Reserve
Reserve
Reserve
Reserve
8
Address Bus
Mode Register
2
4
8
0
~ A
8
2
is
,