GS880Z18/36BT-333/300/250/200/150
Burst Cycles
Although NBT RAMs are designed to sustain 100% bus bandwidth by eliminating turnaround cycle when there is transition from
read to write, multiple back-to-back reads or writes may also be performed. NBT SRAMs provide an on-chip burst address
generator that can be utilized, if desired, to further simplify burst read or write implementations. The ADV control pin, when
driven high, commands the SRAM to advance the internal address counter and use the counter generated address to read or write
the SRAM. The starting address for the first cycle in a burst cycle series is loaded into the SRAM by driving the ADV pin low, into
Load mode.
Burst Order
The burst address counter wraps around to its initial state after four addresses (the loaded address and three more) have been
accessed. The burst sequence is determined by the state of the Linear Burst Order pin (LBO). When this pin is low, a linear burst
sequence is selected. When the RAM is installed with the LBO pin tied high, Interleaved burst sequence is selected. See the tables
below for details.
Mode Pin Functions
Mode Name
Burst Order Control
Output Register Control
Power Down Control
Pin Name
LBO
FT
ZZ
State
L
H
L
H or NC
L or NC
H
Function
Linear Burst
Interleaved Burst
Flow Through
Pipeline
Active
Standby, I
DD
= I
SB
Note:
There is a pull-up device on the FT pin and a pull-down device on the ZZ pin, so this input pin can be unconnected and the chip will operate
in the default states as specified in the above tables.
Burst Counter Sequences
Linear Burst Sequence
A[1:0] A[1:0] A[1:0] A[1:0]
1st address
2nd address
3rd address
4th address
00
01
10
11
01
10
11
00
10
11
00
01
11
00
01
10
Interleaved Burst Sequence
A[1:0] A[1:0] A[1:0] A[1:0]
1st address
2nd address
3rd address
4th address
00
01
10
11
01
00
11
10
10
11
00
01
11
10
01
00
Note:
The burst counter wraps to initial state on the 5th clock.
Note:
The burst counter wraps to initial state on the 5th clock.
BPR 1999.05.18
Rev: 1.02 10/2004
11/24
© 2001, GSI Technology
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
GSI [ GSI TECHNOLOGY ]
