N256S0818HDA/N256S0830HDA
NanoAmp Solutions, Inc.
Control Signal Descriptions
Signal
Name
I/O
Description
A low level selects the device and a high level puts the device in standby mode. If
CS is brought high during a program cycle, the cycle will complete and then the
device will enter standby mode. When CS is high, SO is in high-Z. CS must be
driven low after power-up prior to any sequence being started.
CS
Chip Select
I
Synchronizes all activities between the memory and controller. All incoming
addresses, data and instructions are latched on the rising edge of SCK. Data out is
updated on SO after the falling edge of SCK.
SCK
Serial Clock
I
SI
SO
Serial Data In
Serial Data Out
I
O
Receives instructions, addresses and data on the rising edge of SCK.
Data is transferred out after the falling edge of SCK.
A high level is required for normal operation. Once the device is selected and a
serial sequence is started, this input may be taken low to pause serial communica-
tion without resetting the serial sequence. The pin must be brought low while SCK
is low for immediate use. If SCK is not low, the Hold function will not be invoked
until the next SCK high to low transition. The device must remain selected during
this sequence. SO is high-Z during the Hold time and SI and SCK are inputs are
ignored. To resume operations, HOLD must be pulled high while the SCK pin is
low.
HOLD
Hold
I
Lowering the HOLD input at any time will take to SO output to High-Z.
Functional Operation
Basic Operation
The 256Kb serial SRAM is designed to interface directly with a standard Serial Peripheral Interface (SPI)
common on many standard micro-controllers. It may also interface with other non-SPI ports by
programming discrete I/O lines to operate the device.
The serial SRAM contains an 8-bit instruction register and is accessed via the SI pin. The CS pin must be
low and the HOLD pin must be high for the entire operation. Data is sampled on the first rising edge of
SCK after CS goes low. If the clock line is shared, the user can assert the HOLD input and place the
device into a Hold mode. After releasing the HOLD pin, the operation will resume from the point where it
was held.
The following table contains the possible instructions and formats. All instructions, addresses and data are
transferred MSB first and LSB last.
Instruction Set
Instruction
Instruction Format
Description
READ
WRITE
RDSR
WRSR
0000 0011
0000 0010
0000 0101
0000 0001
Read data from memory starting at selected address
Write data to memory starting at selected address
Read status register
Write status register
6
This is a developmental specification and is subject to change without notice.
NANOAMP [ NANOAMP SOLUTIONS, INC. ]
