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MSM6684B

PIN FUNCTIONS AND OPERATING MODES

• Serial address input (SAD)

Pin used to enter start address for reading/writing. An address can be specified in units of 1024

words. 1024 words of address data can be entered through the pin as 13 bits (A0 to A12) of serial

data. The 13th bit must be A12 as a dummy address, however. The A12 input level must be either

"H" or "L".

• Serial address strobe (SAS)

This is a clock pin for latching serial address data into an internal register.

• Address transfer strobe (TAS)

This is an input pin for loading the internal address counter with serial address data latched in the

address register.

• Read/write clock (RWCK)

This is a clock input pin for reading and writing information in the data register. The trailing edge

of RWCK triggers off internal operation. In the reading mode, information in the data register is

output to the DOUT pin. In the writing mode, the data register is loaded with DIN information.

At the leading edge of RWCK, the internal address counter is incremented automatically by +1.

• Write enable (WE)

This is an input pin for selecting the read mode, the write mode, or the read-modify-write mode.

When WE is "H", the read mode is set up and, when WE is "L", the write mode is set up. When the

level is lowered from "H" to "L" with RWCK active, the read-modify-write mode is set up.

• Data input (DIN)

This is a pin for entering write data. Information on the data input pin is latched when the trailing

edge ofRWCK is encountered in the write mode and that ofWEis encountered in the read/modify

mode.

• Data output (DOUT)

The data output pin always provides high impedance as long as RWCK or CS is kept at "H". When

"H" or "L" information is read, the output pin set at "H" or "L", and information read until RWCK

returns to "H" is held. In the early write mode, the output pin is maintained at high impedance,

so that, connect of DIN and DOUT enables "I/O common operation".

• Chip selection (CS)

This is an input pin for disabling all input pins. This pin allows the use of two or more MSM6684B

devices with data input and output pins connected in parallel.

• Test (TEST, TEST)

The TEST pin must always be fixed at "L" and the TEST pin at "H".