Vizio L37 Service Manual page 48

6. Issue a mode register set command for "DLL reset". The additional 200 cycles of clock
input is required to lock the DLL.(To issue DLL reset command, provide "High" to A8 and
"Low" to BA0)
7. Issue precharge commands for all banks of the device.
8. Issue 2 or more auto-refresh commands.
9. Issue a mode register set command with low to A8 to initialize device operation.
2. Mode Register Set (MRS)
The mode register stores the data for controlling the various operating modes of DDR
SDRAM. It programs CAS latency, 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 register is not defined, therefore the mode register
must be written after EMRS setting for proper DDR SDRAM operation. The mode register
is written by asserting low on CS , RAS , CAS , WE and BA0 (The DDR SDRAM should be
in all bank recharge with CKE already high prior to writing into the mode register). The
state of address pins A0~A11 in the same cycle as CS , RAS , CAS , WE and BA0 going
low is written in the mode register. 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 A0~A2, addressing mode uses A3, CAS latency (read latency from
column address) uses A4~A6. A7 is used for test mode. A8 is used for DLL reset. A7 must
be set to low for normal MRS operation. Refer to the table for specific codes for various
burst length, addressing modes and CAS latencies.
CONFIDENTIAL – DO NOT COPY Page 8-12
File No. SG-0176