Z8 Encore! XP
®
4K Series
Product Specification
34
PA0 and PA6 contain two different timer functions, a timer input and a complementary
timer output. Both of these functions require the same GPIO configuration, the selection
between the two is based on the timer mode. See
for more details.
Direct LED Drive
The Port C pins provide a current sinked output capable of driving an LED without requir-
ing an external resistor. The output sinks current at programmable levels of 3 mA, 7 mA,
13 mA and 20 mA. This mode is enabled through the Alternate Function sub-register
AFS1 and is programmable through the LED control registers. The LED Drive Enable
(LEDEN) register turns on the drivers. The LED Drive Level (LEDLVLH and LEDLVLL)
registers select the sink current.
For correct function, the LED anode must be connected to V
DD
and the cathode to the
GPIO pin.
Using all Port C pins in LED drive mode with maximum current may result in excessive
total current. Refer to the
for the maximum total
current for the applicable package.
Shared Reset Pin
On the 20 and 28-pin devices, the Port D0 pin shares function with a bi-directional reset
pin. Unlike all other I/O pins, this pin does not default to GPIO function on power-up.
This pin acts as a bi-directional reset until user software re-configures it. The Port D0 pin
is output-only when in GPIO mode.
On the 8-pin product versions, the reset pin is shared with PortA2, but the pin is not lim-
ited to output-only when in GPIO mode.
Caution:
If PA2 on the 8-pin product is reconfigured as an input, take care that no external stim-
ulus drives the pin low during any reset sequence. Since PA2 returns to its RESET al-
ternate function during system resets, driving it low will hold the chip in a reset state
until the pin is released. The same applies to the PDO pin on the 28-pin product.
Shared Debug Pin
On the 8-pin version of this device only, the Debug pin shares function with the PortA0
GPIO pin. This pin performs as a general purpose input pin on power-up, but the debug
logic monitors this pin during the reset sequence to determine if the unlock sequence
occurs. If the unlock sequence is present, the debug function is unlocked and the pin no
longer functions as a GPIO pin. If it is not present, the debug feature is disabled until/
unless another reset event occurs. For more details, see
PS022815-0206
General-Purpose I/O
ZILOG [ ZILOG, INC. ]
