CMS4A16LAx–75Ex
Table 3. CAS Latency.
Allowable Operating Frequency (MHz)
Speed
CAS Latency = 1
133MHz
100MHz
≤
50
≤
40
CAS Latency = 2
≤
100
≤
83
CAS Latency = 3
≤
133
≤
100
EXTENDED MODE REGISTER
The Extended Mode Register controls additional functions such
as Partial Array Self Refresh (PASR) and Driver Strength (DS).
The Extended Mode Register is programmed via the Mode
Register Set command (BA1=1, BA0=0) and retains the stored
information until it is programmed again or the device loses
power. The Extended Mode Register must be programmed with
M8 through M11 set to “0”. The Extended Mode Register must
be loaded when all banks are idle and no bursts are in progress,
and the controller must wait the specified time initiating any
subsequent operation. Violating either of these requirements
results in unspecified operation.
AUTO TEMPERATURE COMPENSATED SELF REFRESH
Every cell in the DRAM requires refreshing due to the capacitor
losing its charge over time. The refresh rate is dependent on
temperature. At higher temperatures a capacitor loses charge
quicker than at lower temperatures, requiring the cells to be
refreshed more often. In order to save power consumption,
according to the temperature, Mobile-SDRAM includes the
internal temperature sensor and control units to control the self
refresh cycle automatically.
PARTIAL ARRAY SELF REFRESH
The Partial Array Self Refresh (PASR) feature allows the con-
troller to select the amount of memory that will be refreshed
during SELF REFRESH. The refresh options are all banks
(banks 0, 1, 2, and 3); two banks(banks 0 and 1 or 2 and 3 by
M7); and one bank (bank 0 or 2 by M7). WRITE and READ
commands occur to any bank selected during standard
operation, but only the selected banks in PASR will be
refreshed during SELF REFRESH. The data in the deselected
bank will be lost.
Driver Strength Control
The driver strength feature allows one to reduce the
drive strength of the I/O’s on the device during low frequency
operation. This allows systems to reduce the noise associated
with the I/O’s switching.
EM13-
BA1
1
EM12-
BA0
0
EM11-
A11
EM10-
A10
EM9-
A9
EM8-
A8
EM7-
A7
Bank
Up/Down
EM6-
A6
EM5-
A5
EM4-
A4
0
EM3-
A3
0
EM2-
A2
EM1-
A1
PASR
EM0-
A0
All must be set to ‘0’
Driver Strength
Rev. 0.5, May. ‘07
11
FIDELIX [ FIDELIX ]
