87C196 datasheet(5/34 Pages) INTEL

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87C196KT87C196KS

PIN DESCRIPTIONS (Continued)

Symbol

Name and Function

P55BHE WRH

Byte High Enable or Write High output as selected by the CCR BHEe0 selects the

bank of memory that is connected to the high byte of the data bus A0e0 selects

that bank of memory that is connected to the low byte Thus accesses to a 16-bit

wide memory can be to the low byte only (A0e0 BHEe1) to the high byte only

(A0e1 BHEe0) or both bytes (A0e0 BHEe0) If the WRH function is selected

the pin will go low if the bus cycle is writing to an odd memory location BHE WRH is

only valid during 16-bit external memory write cycles Also an LSIO pin when not

BHEWRH

P56READY

Ready input to lengthen external memory cycles for interfacing with slow or

dynamic memory or for bus sharing If the pin is high CPU operation continues in a

normal manner If the pin is low prior to the falling edge of CLKOUT the memory

controller goes into a wait state mode until the next positive transition in CLKOUT

occurs with READY high When external memory is not used READY has no effect

The max number of wait states inserted into the bus cycle is controlled by the CCR

CCR1 Also an LSIO pin when READY is not selected

P54SLPINT

Dual function IO pin As a bidirectional port pin or as a system function The system

function is a Slave Port Interrupt Output Pin

P62T1CLK

Dual function IO pin Primary function is that of a bidirectional IO pin however it

may also be used as a TIMER1 Clock input The TIMER1 will increment or

decrement on both positive and negative edges of this pin

P63T1DIR

Dual function IO pin Primary function is that of a bidirectional IO pin however it

may also be used as a TIMER1 Direction input The TIMER1 will increment when

this pin is high and decrements when this pin is low

PORT1EPA0 – 7

Dual function IO port pins Primary function is that of bidirectional IO System

function is that of High Speed capture and compare EPA0 and EPA2 have yet

P60 – 61EPA8 – 9

another function of T2CLK and T2DIR of the TIMER2 timercounter

PORT 0ACH0 – 7

8-bit high impedance input-only port These pins can be used as digital inputs andor

as analog inputs to the on-chip AD converter These pins are also used as inputs to

EPROM parts to select the Programming Mode

P63 – 67SSIO

Dual function IO ports that have a system function as Synchronous Serial IO Two

pins are clocks and two pins are data providing full duplex capability

PORT 2

8-bit multi-functional port All of its pins are shared with other functions

PORT 3 and 4

8-bit bidirectional IO ports with open drain outputs These pins are shared with the

multiplexed addressdata bus which has strong internal pullups

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