87C196CB datasheet(11/36 Pages) INTEL

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87C196CB - Automotive

P5.5/BHE#/WRH#

Byte High Enable or Write High output, as selected by the CCR. BHE# = 0 selects the

bank of memory that is connected to the high byte of the data bus. A0 = 0 selects the

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 (A0 = 0, BHE# = 1), to the high byte only (A0 = 1,

BHE# = 0) or both bytes (A0 = 0, BHE# = 0). If the WRH# function is selected, the pin

goes low if the bus cycle is writing to an odd memory location. BHE#/WRH# is only valid

during 16-bit external. Also an LSIO pin when not BHE/WRH#.

P5.4/SLPINT

Dual-function I/O pin. As a bidirectional port pin or as a system function. The system

function is a Slave Port Interrupt Output Pin.

P5.3/RD#

Read signal output to external memory. RD# is active only during external memory reads

or LSIO when not used as RD#.

P5.2/WR#/WRL#

Write and Write Low output to external memory, as selected by the CCR, WR# goes low

for every external write, while WRL# goes low only for external writes where an even

byte is being written. WR#/WRL# is active during external memory writes. Also an LSIO

pin when not used as WR#/WRL#.

P5.1/INST

Output high during an external memory read indicates the read is an instruction fetch.

INST is valid throughout the bus cycle. INST is active only during external memory

fetches, during internal EPROM fetches INST is held low. Also LSIO when not INST.

P5.0/ALE/ADV#

Address Latch Enable or Address Valid output, as selected by CCR. Both pin options

provide a latch to demultiplex the address from the address/data bus. When the pin is

ADV#, it goes inactive (high) at the end of the bus cycle. ADV# can be used as a chip

select for external memory. ALE/ADV# is active only during external memory accesses.

Also LSIO when not used as ALE.

PORT3 and 4

8-bit bidirectional I/O ports with open drain outputs. These pins are shared with the

multiplexed address/data bus which has strong internal pullups.

P2.7/CLKOUT

Output of the internal clock generator. The frequency is the oscillator frequency.

CLKOUT has a 50% duty cycle. Also LSIO pin when not used as CLKOUT.

P2.6/HLDA#

Bus Hold Acknowledge. Active-low output indicates that the bus controller has

relinquished control of the bus. Occurs in response to an external device asserting the

HLD# signal. Also LSIO when not used as HLDA#.

P2.5/HLD#

Bus Hold. Active-low signal indicates that an external device is requesting control of the

bus. Also LSIO when not used as HLD#.

P2.4/INTOUT#

Interrupt Output. This active-low output indicates that a pending interrupt requires use of

the external bus. Also LSIO when not used as INTOUT#.

P2.3/BREQ#

Bus Request. This active-low output signal is asserted during a HOLD cycle when the bus

controller has a pending external memory cycle. Also LSIO when not used as BREQ#.

P2.2/EXTINT

A positive transition on this pin causes a maskable interrupt vector through memory

location 203CH. Also LSIO when not used as EXTINT.

P2.1/RXD

Receive data input pin for the Serial I/O port. Also LSIO if not used as RXD.

P2.0/TXD

Transmit data output pin for the Serial I/O port. Also LSIO if not used as TXD.

PORT 1/EPA0–7

Dual-function I/O port pins. Primary function is that of bidirectional I/O. System function is

that of High Speed capture and compare. EPA0 and EPA2 have another function of

T2CLK and T2DIR of the TIMER2 timer/counter.

PORT 0/ACH0–7

8-bit high impedance input-only port. These pins can be used as digital inputs and/or as

analog inputs to the on-chip A/D converter. These pins are also used as inputs to

EPROM parts to select the Programming Mode.

EPORT

8-bit bidirectional standard and I/O Port. These bits are shared with the extended

address bus, A16–A19 for CB PLCC, A16–A23 for CB QFP. Pin function is selected on a

per pin basis.

TXCAN

Push-pull output to the CAN bus line.

RXCAN

High impedance input-only from the CAN bus line.

Table 3. Pin Descriptions (Sheet 2 of 2)

Name

Description

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