EE80C251TB24 Datasheet, PDF (15/36 Pages) Intel Corporation – HIGH-PERFORMANCE CHMOS MICROCONTROLLER

8xC251TB/TQ HIGH-PERFORMANCE CHMOS MICROCONTROLLER
Signal
Name
RD#
RST
RXD
RXD1
T1:0
T2
T2EX
TXD
TXD1
V_CC
V_CC2
V_SS
V_SS1
V_SS2
Table 6. Signal Descriptions (Sheet 2 of 3)
Type
O
I
I/O
I/O
I
I/O
I
O
O
PWR
PWR
GND
GND
GND
Description
Read or 17th Address Bit (A16). Read signal output to external data
memory or 17th external address bit (A16), depending on the values of
bits RD0 and RD1 in configuration byte UCONFIG0. (See PSEN#).
Reset. Reset input to the chip. Holding this pin high for 64 oscillator
periods while the oscillator is running resets the device. The port pins are
driven to their reset conditions when a voltage greater than V_IH1 is
applied, whether or not the oscillator is running. This pin has an internal
pulldown resistor, which allows the device to be reset by connecting a
capacitor between this pin and V_CC.
Asserting RST when the chip is in idle mode or powerdown mode returns
the chip to normal operation.
Receive Serial Data. RXD sends and receives data in serial I/O mode 0
and receives data in serial I/O modes 1, 2, and 3.
Receive Serial Data 1. RXD1 sends and receives data in serial I/O
mode 0 and receives data in serial I/O modes 1, 2, and 3 for the 2nd
serial port.
Timer 1:0 External Clock Inputs. When timer 1:0 operates as a counter,
a falling edge on the T1:0 pin increments the count.
Timer 2 Clock Input/Output. For the timer 2 capture mode, this signal is
the external clock input. For the clock-out mode, it is the timer 2 clock
output.
Timer 2 External Input. In timer 2 capture mode, a falling edge initiates a
capture of the timer 2 registers. In auto-reload mode, a falling edge
causes the timer 2 registers to be reloaded. In the up-down counter
mode, this signal determines the count direction: 1 = up, 0 = down.
Transmit Serial Data. TXD outputs the shift clock in serial I/O mode 0
and transmits serial data in serial I/O modes 1, 2, and 3.
Transmit Serial Data 1. TXD1 outputs the shift clock in serial I/O mode 0
and transmits serial data in serial I/O modes 1, 2, and 3 for the 2nd serial
port.
Supply Voltage. Connect this pin to the +5V supply voltage.
Secondary Supply Voltage 2. This supply voltage connection is
provided to reduce power supply noise. Connection of this pin to the +5V
supply voltage is recommended. However, when using the 8XC251SB as
a pin-for-pin replacement for the 8XC51FX, V_SS2 can be unconnected
without loss of compatibility. (Not available on DIP)
Circuit Ground. Connect this pin to ground.
Secondary Ground. This ground is provided to reduce ground bounce
and improve power supply bypassing. Connection of this pin to ground is
recommended. However, when using the 8xC251TB/TQ as a pin-for-pin
replacement for the 8XC51BH, V_SS1 can be unconnected without loss of
compatibility. (Not available on DIP)
Secondary Ground 2. This ground is provided to reduce ground bounce
and improve power supply bypassing. Connection of this pin to ground is
recommended. However, when using the 8xC251TB/TQ as a pin-for-pin
replacement for the 8XC51FX, V_SS2 can be unconnected without loss of
compatibility. (Not available on DIP)
Alternate
Function
P3.7/A16
—
P3.0
P1.2/ECI
P3.5:4
P1.0
P1.1
P3.1
P1.3/CEX0
—
—
—
—
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