I/O PORTS

P5.0/ALE

If EA# is high on reset (internal access), the pin is weakly held high

 

 

until your software writes to P5_MODE. If EA# is low on reset

 

 

(external access), either ALE or ADV# is activated as a system

 

 

control pin, depending on the ALE bit of CCR0. In either case, the

 

 

pin becomes a true complementary output.

P5.1/INST

This pin remains weakly held high until your software writes config-

 

 

uration data into P5_MODE.

P5.2/WR#/WRL#

This pin remains weakly held high until your software writes config-

 

 

uration data into P5_MODE.

P5.3/RD#

If EA# is high on reset (internal access), the pin is weakly held high

 

 

until your software writes to P5_MODE. If EA# is low on reset

 

 

(external access), RD# is activated as a system control pin and the

 

 

pin becomes a true complementary output.

P5.4

This pin is weakly held high until your software writes to

 

 

P5_MODE. P5.4 is the enable pin for ONCE mode (see Chapter 14,

 

 

“Special Operating Modes”) and one of the enable pins for Intel-

 

 

reserved test modes. Because a low input during reset could cause the

 

 

device to enter ONCE mode or a reserved test mode, exercise

 

 

caution if you use this pin for input. Be certain that your system

 

 

meets the VIH specification (listed in the datasheet) during reset to

 

 

prevent inadvertent entry into ONCE mode or a test mode.

P5.5/BHE#/WRH#

This pin is weakly held high until the CCB fetch is completed. At

 

 

that time, the state of this pin depends on the value of the BW0 bit of

 

 

the CCRs. If BW0 is clear, the pin remains weakly held high until

 

 

your software writes to P5_MODE. If BW0 is set, BHE# is activated

 

 

as a system control pin and the pin becomes a true complementary

 

 

output.

P5.6/READY

This pin remains weakly held high until the CCB fetch is completed.

 

 

At that time, the state of this pin depends on the value of the IRC0–

 

 

IRC2 bits of the CCRs. If IRC0–IRC2 are all set (111B), READY is

 

 

activated as a system control pin. This prevents the insertion of

 

 

infinite wait states upon the first access to external memory. For any

 

 

other values of IRC0–IRC2, the pin is configured as I/O upon reset.

 

 

NOTE: If IRC0–IRC2 of the CCB are all set (activating READY as

 

 

a system control pin) and P5_MODE.6 is cleared (config-

 

 

uring the pin as I/O), an external memory access may cause

 

 

the processor to lock up.

P5.7/BUSWIDTH

This pin remains weakly held high until your software writes config-

 

 

uration data into P5_MODE.

 

 

6-13

 

 

 

 

 

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Intel 8XC196MH, 8XC196MD, 8XC196MC manual P5.1/INST