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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
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.
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#.
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
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.
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 (Note 3) (Note 3)
P2.0 TXD WK1 (Note 3) (Note 3)
P2.1 RXD WK1 (Note 3) (Note 3)
Table A-3. Signal Descriptions (Continued)
Name Type Description