
Device Operations 
  A43P26161 
PRELIMINARY 
 (July, 2005, Version 1.1) 
11 
AMIC Technology, Corp.
Clock (CLK) 
The clock input is used as the reference for all SDRAM 
operations. All operations are synchronized to the positive 
going edge of the clock. The clock transitions must be 
monotonic between VIL and VIH. During operation with CKE 
high all inputs are assumed to be in valid state (low or high) 
for the duration of set up and hold time around positive edge 
of the clock for proper functionality and ICC specifications. 
Clock Enable (CKE) 
The clock enable (CKE) gates the clock onto SDRAM. If 
CKE goes low synchronously with clock (set-up and hold 
time same as other inputs), the internal clock is suspended 
from the next clock cycle and the state of output and burst 
address is frozen as long as the CKE remains low. All other 
inputs are ignored from the next clock cycle after CKE goes 
low. When all banks are in the idle state and CKE goes low 
synchronously with clock, the SDRAM enters the power 
down mode from the next clock cycle. The SDRAM remains 
in the power down mode ignoring the other inputs as long as 
CKE remains low. The power down exit is synchronous as 
the internal clock is suspended. When CKE goes high at 
least “t
SS
 + 1 
CLOCK
” before the high going edge of the 
clock, then the SDRAM becomes active from the same clock 
edge accepting all the input commands. 
Bank Select (BS0, BS1) 
This SDRAM is organized as 4 independent banks of 
1,048,576 words X 16 bits memory arrays. The BS0, BS1 
inputs is latched at the time of assertion of 
RASand 
CAS
to select the bank to be used for the operation. The bank 
select BS0, BS1 is latched at bank activate, read, write 
mode register set and precharge operations. 
Address Input (A0 ~ A11) 
The 20 address bits required to decode the 1,048,576 word 
locations are multiplexed into 12 address input pins 
(A0~A11). The 12 bit row address is latched along with 
RAS, BS0 and BS1 during bank activate command. The 8 
bit column address is latched along with 
CAS
 , 
WE
 , BS0 
and BS1during read or write command. 
NOP and Device Deselect 
When RAS , 
CAS
performs no operation (NOP). NOP does not initiate any new 
operation, but is needed to complete operations which 
require more than single clock like bank activate, burst read, 
auto refresh, etc. The device deselect is also a NOP and is 
entered by asserting 
CS
high. 
CS
command decoder so that RAS , 
CAS
  and 
WE
 , and all 
the address inputs are ignored. 
 and 
WE
are high, the SDRAM 
 high disables the 
Power-Up 
The following sequence is recommended for POWER UP 
1. Power must be applied to either CKE and DQM inputs to 
pull them high and other pins are NOP condition at the 
inputs before or along with VDD (and VDDQ) supply. 
The clock signal must also be asserted at the same time. 
2. After VDD reaches the desired voltage, a minimum pause 
of 200 microseconds is required with inputs in NOP 
condition. 
3. All banks must be precharged now. 
4. Perform a minimum of 2 Auto refresh cycles to stabilize 
the internal circuitry. 
5. Perform a MODE REGISTER SET cycle to program the 
CAS latency, burst length and burst type as the default 
value of mode register is undefined. 
At the end of one clock cycle from the mode register set 
cycle, the device is ready for operation. 
When the above sequence is used for Power-up, all the 
out-puts will be in high impedance state. The high 
impedance of outputs is not guaranteed in any other 
power-up sequence. 
cf.) Sequence of 4 & 5 may be changed. 
Mode Register Set (MRS) 
The mode register stores the data for controlling the various 
operation modes of SDRAM. It programs the CAS latency, 
addressing mode, burst length, test mode and various 
vendor specific options to make 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 power up to operate the SDRAM. The mode register is 
written by asserting low on 
CS
 ,RAS , 
CAS
 ,
 WE
 (The 
SDRAM should be in active mode with CKE already high 
prior to writing the mode register). The state of address pins 
A0~A11, 
BS0 
and 
BS1 
CS
 ,RAS,
CAS
 ,
WE
going low is the data written in the 
mode register. One clock cycle is required to complete the 
write 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 field uses 
A0~A2, burst type uses A3, addressing mode uses A4~A6, 
A7~A8, A9, BS0 and BS1 are used for vendor specific 
options or test mode. And the write burst length is 
programmed using A9. A7~A8, A10~A11, BS0 and BS1 
must be set to low for normal SDRAM operation.  
Refer to table for specific codes for various burst length, 
addressing modes and CAS latencies. BS0 and BS1 have to 
be set to “0” to enter the Mode Register. 
in 
the 
same 
cycle 
as 
Extended Mode Register (EMRS)  
The Extended Mode Register controls functions beyond 
those controlled by the Mode Register. These additional 
functions are unique to AMIC’s Low Power SDRAM and 
includes a Refresh Period field (TCSR) for temperature 
compensated self-refresh and a Partial-Array Self Refresh 
field (PASR). The PASR field is used to specify whether only 
bank A and bank B,or bank A,or 1/2 of bank A,or 1/4 of bank 
A be refreshed. Disable banks will not be refreshed in Self-
Refresh mode and written data will be lost. When only bank 
A is selected it is possible to partial select only half or one 
quarter of bank A. The TCR field has four entries to set 
Refresh Period during self-refresh depending on the case 
temperature of the Low Power devices.  
The Extended Mode Register is programmed via the Mode 
Register Set command (with BS0=0 and BS1=1) and retains