GMS90C320PL40 datasheet(11/46 Pages) HYNIX

11 / 46 page

GMS90C320

OCT. 2000 Ver 1.2

P2.0-P2.7

24-31

21-28

18-25

I/O

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2

pins that have 1s written to them are pulled high by the internal

pull-up resistors and can be used as inputs. As inputs, port 2 pins

that are externally pulled low will source current because of the

pulls-ups (IIL, in the DC characteristics). Port 2 emits the high-

order address byte during fetches from external program memory

and during accesses to external data memory that use 16-bit

addresses (MOVX @DPTR). In this application it uses strong

internal pull-ups when emitting 1s. During accesses to external

data memory that use 8-bit addresses (MOVX @Ri), port 2 emits

the contents of the P2 special function register.

PSEN

The Program Store Enable

The read strobe to external program memory when the device is

executing code from the external program memory. PSEN is acti-

vated twice each machine cycle, except that two PSEN activation

are skipped during each access to external data memory. PSEN

is not activated during fetches from internal program memory.

RESET

A high level on this pin for two machine cycles while the oscillator

is running resets the device. An internal diffused resistor to VSS

permits power-on reset using only an external capacitor to VCC.

ALE

The Address Latch Enable

Output pulse for latching the low byte of the address during an

access to external memory. In normal operation, ALE is emitted

at a constant rate of 1/6 the oscillator frequency, and can be used

for external timing or clocking. Note that one ALE pulse is skipped

during each access to external data memory.

External Access Enable

EA must be external held low to enable the device to fetch code

from external program memory locations 0000H to FFFFH.If EA is

held high, the device executes from internal program memory

unless the program counter contains an address greater than its

internal memory size.

P0.0-P0.7

43-36

39-32

37-30

I/O

Port 0

Port 0 is an 8-bit open-drain bidirectional I/O port. Port 0 pins that

have 1s written to them float and can be used as high-impedance

inputs. Port 0 is also the multiplexed low-order address and data

bus during accesses to external program and data memory. In

this application it uses strong internal pull-ups when emitting 1s.

Port 0 also outputs the code bytes during program verification in

the GMS97C5x. External pull-up resistors are required during

program verification.

VSS

Circuit ground potential

VCC

Supply terminal for all operating modes

N.C.

1,12,

23,34

6,17,

28,39

No connection

Symbol

Pin Number

Input/

Output

Function

P-LCC-44

P-DIP-40

P-MQFP-

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