KSI-W001-000

5

Pin Description(continued)

ALE

: PIN 30 (DIP40), PIN 33 (PLCC44)

Address latch enable output pulse for latching the low byte of the address during

accesses to external memory.

In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency,

and may be used for external timing of clocking purposes.

Note : However, that one ALE pulse is skipped during each access to external data

memory.

If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH.

With the bit set, ALE is active only during a MOVX instruction. Otherwise, the pin

is weakly pulled high.

PSEN : PIN 29 (DIP40), PIN 32 (PLCC44)

Program store enable is the read strobe to external program memory. When the

60C51 is executing code from external program memory, PSEN is activated twice

each machine cycle, except that two PSEN activations are skipped during each

access to external data memory. PSEN is not activated during fetches from internal

program memory.

EA

: PIN 31 (DIP40), PIN 35 (PLCC44)

to fetch code from external program memory locations starting at 0000H up to

FFFFH.

the program counter contains an address greater than 0FFFH.

XTAL1 : PIN 19 (DIP40), PIN 21 (PLCC44)

Input to the inverting oscillator amplifier and input to the internal clock generator

circuits.

NC

: PIN1, 12, 23, 34 (PLCC44)

Non connection pins.

XTAL2 : PIN 18 (DIP40), PIN 20(PLCC44)

Output from the inverting oscillator amplifier

SD60C31/P SD60C51/P