Datasheet

t
REFI
and t
RFC
parameters
The default Refresh rate mode is fixed 1x mode where Refresh commands should be issued with the
normal rate, i.e., t
REFI
1 = t
REFI(base)
(for T
CASE
≤ 85°C), and the duration of each refresh command is the normal
refresh cycle time (t
RFC
1). In 2x mode (either fixed 2x or on-the-fly 2x mode), Refresh commands should be
issued to the device at the double frequency (t
REFI
2 = t
REFI(base)
/2) of the normal Refresh rate. In 4x mode,
Refresh command rate should be quadrupled (t
REFI
4 = t
REFI(base)
/4). Per each mode and command type, t
RFC
parameter has different values as defined in the following table.
The refresh command that should be issued at the normal refresh rate and has the normal refresh cycle
duration may be referred to as a REF1x command. The refresh command that should be issued at the double
frequency (t
REFI
2 = t
REFI(base)
/2) may be referred to as a REF2x command. Finally, the refresh command that
should be issued at the quadruple rate (t
REFI
4 = t
REFI(base)
/4) may be referred to as a REF4x command.
In the Fixed 1x Refresh rate mode, only REF1x commands are permitted. In the Fixed 2x Refresh rate
mode, only REF2x commands are permitted. In the Fixed 4x Refresh rate mode, only REF4x commands are
permitted. When the on-the-fly 1x/2x Refresh rate mode is enabled, both REF1x and REF2x commands are
permitted. When the on-the-fly 1x/4x Refresh rate mode is enabled, both REF1x and REF4x commands are
permitted.
Table 19. Refresh command truth table
Refresh Mode
Parameter
4Gb
Unit
t
REFI(base)
7.8
μS
1x mode
t
REFI
1
-40°C ≤ T
CASE
≤ 85°C
t
REFI(base)
μS
85°C ≤ T
CASE
≤ 95°C
t
REFI(base)
/2
μS
t
RFC
1(min)
260
ns
2x mode
t
REFI
2
-40°C ≤ T
CASE
≤ 85°C
t
REFI(base)
/2
μS
85°C ≤ T
CASE
≤ 95°C
t
REFI(base)
/4
μS
t
RFC
2(min)
160
ns
4X mode
t
REFI
4
-40°C ≤ T
CASE
≤ 85°C
t
REFI(base)
/4
μS
85°C ≤ T
CASE
≤ 95°C
t
REFI(base)
/8
μS
t
RFC
4(min)
110
ns
AS4C512M8D4
Confidential
- 40 of 196 -
Rev.1.0. Aug.2019