Intel 87C196CB Manual De Usuario
87C196CB Supplement
A-14
A.3
DEFAULT CONDITIONS
Table A-5 lists the default functions of the I/O and control pins of the microcontroller with their
values during various operating conditions. Table A-4 defines the symbols used to represent the
pin status. Refer to the DC Characteristics table in the datasheet for actual specifications for V
values during various operating conditions. Table A-4 defines the symbols used to represent the
pin status. Refer to the DC Characteristics table in the datasheet for actual specifications for V
OL
,
V
IL
, V
OH
, and V
IH
.
WRL#
O
Write Low
†
During 16-bit bus cycles, this active-low output signal is asserted for low-byte
writes and word writes. During 8-bit bus cycles, WRL# is asserted for all write
operations.
writes and word writes. During 8-bit bus cycles, WRL# is asserted for all write
operations.
WRL# is multiplexed with P5.2, SLPWR#, and WR#.
†
The chip configuration register 0 (CCR0) determines whether this pin
functions as WR# or WRL#. CCR0.2 = 1 selects WR#; CCR0.2 = 0 selects
WRL#.
WRL#.
XTAL1
I
Input Crystal/Resonator or External Clock Input
Input to the on-chip oscillator and the internal clock generators. The internal
clock generators provide the peripheral clocks, CPU clock, and CLKOUT
signal. When using an external clock or crystal instead of the on-chip oscillator,
connect the clock input to XTAL1. The external clock signal must meet the V
clock generators provide the peripheral clocks, CPU clock, and CLKOUT
signal. When using an external clock or crystal instead of the on-chip oscillator,
connect the clock input to XTAL1. The external clock signal must meet the V
IH
specification for XTAL1 (see datasheet).
XTAL2
O
Inverted Output for the Crystal/Resonator
Output of the on-chip oscillator inverter. Leave XTAL2 floating when the design
uses a external clock source instead of the on-chip oscillator.
uses a external clock source instead of the on-chip oscillator.
Table A-4. Definition of Status Symbols
Symbol
Definition
Symbol
Definition
0
Voltage less than or equal to V
OL
, V
IL
MD0
Medium pull-down
1
Voltage greater than or equal to V
OH
, V
IH
MD1
Medium pull-up
HiZ
High impedance
WK0
Weak pull-down
LoZ0
Low impedance; strongly driven low
WK1
Weak pull-up
LoZ1
Low impedance; strongly driven high
ODIO
Open-drain I/O
Table A-5. 87C196CB Pin Status
Port Pins
Multiplexed
With
Status During
Reset
Status During
Idle
Status During
Powerdown
P0.7:4
ACH7:4
HiZ
HiZ
HiZ
P1.7:0
EPA7:0
WK1
P2.0
TXD
WK1
P2.1
RXD
WK1
Table A-3. Signal Descriptions (Continued)
Name
Type
Description