8XC196NP COMMERCIAL CHMOS 16-BIT MICROCONTROLLER
Name
TXD
VCC
VSS
WR#
WRH#
WRL#
XTAL1
XTAL2
Table 8. Pin Descriptions (Continued)
Type
Description
Multiplexed
with
O Transmit Serial Data
P2.0
In serial I/O modes 1, 2, and 3, TXD is used to transmit serial port
data. In mode 0, it is used as the serial clock output.
PWR Digital Supply Voltage
—
Connect each VCC pin to the digital supply voltage.
GND Digital Circuit Ground
—
Connect each VSS pin to ground through the lowest possible
impedance path.
O Write
WRL#
This active-low output indicates that an external write is occurring.
This signal is asserted only during external memory writes.
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#.
O Write High
BHE#
During 16-bit bus cycles, this active-low output signal is asserted for
high-byte writes and word writes to external memory. During 8-bit
bus cycles, WRH# is asserted for all write operations.
The chip configuration register 0 (CCR0) determines whether this
pin functions as BHE# or WRH#. CCR0.2=1 selects BHE#;
CCR0.2=0 selects WRH#.
O Write Low
WR#
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.
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#.
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 source instead
of the on-chip oscillator, connect the clock input to XTAL1. The
external clock signal must meet the VIH specification for XTAL1.
O Inverted Output for the Crystal/Resonator
—
Output of the on-chip oscillator inverter. Leave XTAL2 floating when
the design uses an external clock source instead of the on-chip
oscillator.
ELECTRICAL CHARACTERISTICS
16