Z8F042AHJ020SG Datasheet, PDF (55/282 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
38
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 the Timers chapter on page 70 for more
details.
Caution: For pins with multiple alternate functions, Zilog recommends writing to the AFS1 and
AFS2 subregisters before enabling the alternate function via the AF subregister. As a re-
sult, spurious transitions through unwanted alternate function modes will be prevented.
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 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. See the Electrical Characteristics chapter on page 226 for the max-
imum total current for the applicable package.
Shared Reset Pin
On the 20- and 28-pin devices, the PD0 pin shares function with a bidirectional reset pin.
Unlike all other I/O pins, this pin does not default to GPIO function on power-up. This pin
acts as a bidirectional input/open-drain output reset until the software reconfigures it. The
PD0 pin is an output-only open drain when in GPIO mode. There are no pull-up, High
Drive, or Stop Mode Recovery source features associated with the PD0 pin.
On the 8-pin product versions, the reset pin is shared with PA2, but the pin is not limited to
output-only when in GPIO mode.
Caution: If PA2 on the 8-pin product is reconfigured as an input, ensure that no external stimulus
drives the pin low during any reset sequence. Since PA2 returns to its RESET alternate
function during system resets, driving it Low holds the chip in a reset state until the pin
is released.
PS022827-1212
PRELIMINARY
Direct LED Drive