Internet Data Sheet
HYB18H256321BF
256-Mbit GDDR3
3.1.1
Burst length
Read and Write accesses to the GDDR3 Graphics RAM are burst oriented with burst length of 4 and 8. This value must be
programmed using the Mode Register Set command (A0 .. A2). The burst length determines the number of column locations
that can be accessed for a given READ or WRITE command.
When a READ or WRITE command is issued, a block of columns equal to the burst length is effectively selected. All accesses
for that burst take place within this block if a boundary is reached. The starting location within this block is determined by the
two least significant bits A0 and A1 which are set internally to the fixed value of zero each.Reserved states should not be used,
as unknown operation or incompatibility with future versions may result.
3.1.2
Burst type
Accesses within a given bank must be programmed to be sequential. This is done using the Mode Register Set command (A3).
This device does not support the burst interleave mode.
TABLE 6
Burst Definition
Burst Length
Starting Column Address Order of Accesses within a Burst
(Type = sequential)
A2 A1 A0
4
8
—
0
X
X
X
X
X
X
0-1-2-3
0-1-2-3-4-5-6-7
4-5-6-7-0-1-2-3
1
The value applied at the balls A0 and A1 for the column address is “Don’t care”.
3.1.3
CAS Latency
The CAS latency is the delay, in clock cycles, between the registration of a READ command and the availability of the first bit
of output data.
If a READ command is registered at clock edge n, and the latency is m clocks, the data will be available nominally coincident
with clock edge n+m.
The two Mode Register setups support different CAS Latencies in terms of clock cycles. The mid-range-speed Mode Register
supports latencies from 7 to 14. The high-speed Mode Register supports latencies from 10 to 17. The active Mode Register
setup is selected by Bit0 of EMRS2.
3.1.4
Write Latency
The WRITE latency, WL, is the delay, in clock cycles, between the registration of a WRITE command and the availability of the
first bit of input data.
Rev. 0.80, 2007-09
14
09132007-07EM-7OYI
QIMONDA [ QIMONDA AG ]
