M65KA128AL datasheet(10/53 Pages) STMICROELECTRONICS

10 / 53 page

Signal descriptions

M65KA128AL

10/53

2.8

Clock Input (K)

The Clock signal, K, is used to clock the Read and Write cycles. During normal operation,

the Clock Enable pin, KE, is High, VIH. The clock signal K can be suspended to switch the

device to the Self Refresh, Power-Down or Deep Power-Down mode by driving KE Low, VIL.

2.9

Clock Enable (KE)

The Clock Enable, KE, pin is used to control the synchronizing of the signals to Clock signal

K. The signals are clocked when KE is High, VIH When KE is Low, VIL, the signals are no

longer clocked and data Read and Write cycles are extended. KE is also involved in

switching the device to the Self Refresh, Power-Down and Deep Power-Down modes.

2.10

Lower/Upper Data Input/Output Mask (LDQM/UDQM)

Lower Data Input/Output Mask and Upper Data Input/Output Mask pins are input signals

used to control the Input and Output buffers, respectively.

During Read operations, LDQM and UDQM control the Output buffer. When both LDQM and

UDQM are High, VIH, the Output buffer is disabled. When held Low, VIL, the Output buffer is

enabled. LDQM and UDQM are used to mask the data read or written from or to the

memory array. LDQM Low, VIL, gates the data from or to the Lower Byte Data I/O (DQ0 to

DQ7) while UDQM Low, gates the data from or to the Upper Byte Data I/Os (DQ8 to DQ15).

During read operations, the latency between LDQM/UDQM High or Low and data output

disabled or enabled is two clock cycles. During write operations, there is no latency between

LDQM/UDQM stable and data input valid.

2.11

VDD Supply Voltage

VDD provides the power supply to the internal core of the memory device. It is the main

power supply for all operations (Read and Write).

2.12

VDDQ Supply Voltage

VDDQ provides the power supply to the I/O pins and enables all Outputs to be powered

independently of VDD. VDDQ can be tied to VDD or can use a separate supply.

It is recommended to power-up and power-down VDD and VDDQ together to avoid certain

conditions that would result in data corruption.

2.13

VSS Ground

Ground, VSS, is the reference for the core power supply. It must be connected to the system

ground.

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