Rainbow Electronics T89C5121 - Manual (Page 8)

8
A/T8xC5121
4164G–SCR–07/06
RST V
CC
I/O Reset input
Holding this pin low for 64 oscillator periods while the oscillator
is running resets the device. The Port pins are driven to their reset
conditions when a voltage lower than V
IL
is applied, whether or
not the oscillator is running.
This pin has an internal pull-up resistor which allows the device to be reset by
connecting a capacitor between this pin and VSS.This capacitor is optional
thanks to the internal POR which output a Reset as long as Vcc has not
reached the POR threshold level
Asserting RST when the chip is in Idle mode or Power-down mode
returns the chip to normal operation.
The output is active for at least 12 oscillator periods when an internal
reset occurs.
XTAL1 V
CC
I Input to the on-chip inverting oscillator amplifier
To use the internal oscillator, a crystal/resonator circuit is connected
to this pin.
If an external oscillator is used, its output is connected to this pin.
XTAL2 V
CC
O Output of the on-chip inverting oscillator amplifier
To use the internal oscillator, a crystal/resonator circuit is connected
to this pin.
If an external oscillator is used, XTAL2 may be left unconnected.
V
CC
PWR Supply voltage
V
CC
is used to power the internal voltage regulators and internal I/O’s.
LI PWR DC/DC input
LI must be tied to V
CC
through an external coil (typically 4, 7 μ H) and provide
the current for the pump charge of the DC/DC converter.
CV
CC
PWR Card Supply voltage
CV
CC
is the programmable voltage output for the Card interface.
It must be connected to an external decoupling capacitor.
DV
CC
PWR Digital Supply voltage
DV
CC
is used to supply the digital core and internal I/Os. It is
internally connected to the output of a 3V regulator and must be connected to
an external decoupling capacitor.
EV
CC
V
CC
PWR Extra supply voltage
EV
CC
is used to supply the level shifters of UART interface I/O
pins. It must be connected to an external decoupling capacitor.
This reference voltage is generated internally (automatically or not),
or it can be connected to an external voltage reference.
CVSS GND DC/DC ground
CVSS is used to sink high shunt currents from the external coil.
VSS GND Ground
Table 1. Ports Description (Continued)
Port
Signal
Name Alternate
Internal
Power
Supply ESD Type Description