AS4C8M16SA-Automotive
6
Write command
(RAS# = "H", CAS# = "L", WE# = "L", BAs = Bank, A10 = "L", A0-A8 = Column Address)
The Write command is used to write a burst of data on consecutive clock cycles from an active row
in an active bank. The bank must be active for at least tRCD (min.) before the Write command is issued.
During write bursts, the first valid data-in element will be registered coincident with the Write command.
Subsequent data elements will be registered on each successive positive clock edge (refer to the
following figure). The DQs remain with high-impedance at the end of the burst unless another command
is initiated. The burst length and burst sequence are determined by the mode register, which is already
programmed. A full-page burst will continue until terminated (at the end of the page it will wrap to column
0 and continue).
T0
T1
T2
T3
T4
T5
T6
T7
T8
CLK
NOP
WRITE A
DIN A0
NOP
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
don’t care
DIN A1
DIN A2
DIN A3
DQ
The first data element and the write
are registered on the same clock edge
Figure 10. Burst Write Operation
(Burst Length = 4)
A write burst without the auto precharge function may be interrupted by a subsequent Write,
BankPrecharge/PrechargeAll, or Read command before the end of the burst length. An interrupt coming
from Write command can occur on any clock cycle following the previous Write command (refer to the
following figure).
T0
T1
T2
T3
T4
T5
T6
T7
T8
CLK
NOP
WRITE A
DIN A0
WRITE B
DIN B0
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
DQ
DIN B1
DIN B2
DIN B3
Figure 11. Write Interrupted by a Write
(Burst Length = 4)
The Read command that interrupts a write burst without auto precharge function should be issued
one cycle after the clock edge in which the last data-in element is registered. In order to avoid data
contention, input data must be removed from the DQs at least one clock cycle before the first read data
appears on the outputs (refer to the following figure). Once the Read command is registered, the data
inputs will be ignored and writes will not be executed.
Confidential
10
Rev. 2.0
Mar. /2015
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
