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B-21
SIGNAL DESCRIPTIONS
SCLK1:0#
(MH only)
I/O Shift Clock 0 and 1
In SIO mode 4, SCLK
x
# are bidirectional shift clock signals that synchronize the
serial data transfer. The DIR bit in the SP_CON register controls the direction of
SCLK
x
#.
DIR = 1 allows an external shift clock to be input on SCLK
x
#.
DIR = 0 causes SCLK
x
# to output the internal shift clock.
SCLK0# is multiplexed with P2.1, BCLK0, and PALE#. SCLK1# is multiplexed
with P2.7 and BCLK1.
T1CLK I Timer 1 External Clock
External clock for timer 1. Timer 1 increments (or decrements) on both rising
and falling edges of T1CLK. Also used in conjunction with T1DIR for
quadrature counting mode.
and
External clock for the serial I/O baud-rate generator input (program selectable).
On the 8XC196MC and MD, T1CLK is multiplexed with P1.2 and ACH10. On
the 8XC196MH, T1CLK is multiplexed with P0.6, ACH6, and PMODE.2.
T1DIR I Timer 1 External Direction
External direction (up/down) for timer 1. Timer 1 increments when T1DIR is high
and decrements when it is low. Also used in conjunction with T1CLK for
quadrature counting mode.
On the 8XC196MC and MD, T1DIR is multiplexed with P1.3 and ACH11. On the
8XC196MH, T1DIR is multiplexed with P0.7, ACH7, and PMODE.3.
TXD1:0
(MH only)
O Transmit Serial Data 0 and 1
In serial I/O modes 1, 2, and 3, TXD0 and 1 transmit serial port output data. In
mode 0, they are the serial clock outputs.
TXD0 is multiplexed with P1.0 and TXD1 is multiplexed with P1.2.
TXD0 and 1 are not implemented on the 8XC196MC and MD.
V
CC
PWR Digital Supply Voltage
Connect each V
CC
pin to the digital supply voltage.
V
PP
PWR Programming Voltage
During programming, the V
PP
pin is typically at +12.5 V (V
PP
voltage).
Exceeding the maximum V
PP
voltage specification can damage the device.
V
PP
also causes the device to exit powerdown mode when it is driven low for at
least 50 ns. Use this method to exit powerdown only when using an external
clock source because it enables the internal phase clocks, but not the internal
oscillator. See “Driving the Vpp Pin Low” on page 14-6.
On devices with no internal nonvolatile memory, connect V
PP
to V
CC
.
V
REF
PWR Reference Voltage for the A/D Converter
This pin also supplies operating voltage to both the analog portion of the A/D
converter and the logic used to read port 0 (also port 1 in the 8XC196MC and
8XC196MD).
V
SS
GND Digital Circuit Ground
These pins supply ground for the digital circuitry. Connect each V
SS
pin to
ground through the lowest possible impedance path.
Table B-6. Signal Descriptions (Continued)
Name Type Description