ATA6020N ATMEL Corporation, ATA6020N Datasheet - Page 22

• Manufacturer Part Number: ATA6020N
• Description: Low-current Microcontroller For Watchdog Function
• Manufacturer: ATMEL Corporation

5.2
5.2.1
Figure 5-2.
22
Bi-directional Ports
ATA6020N
Bi-directional Port 2
Bi-directional Port 2
I/O Bus
I/O Bus
Master reset
I/O Bus
Ports 2, 4 and 5 are 4 bits wide. All ports may be used for data input or output. All ports are
equipped with Schmitt trigger inputs and a variety of mask options for open-drain, open-source,
full-complementary outputs, pull-up and pull-down transistors. All Port Data Registers (PxDAT)
are I/O mapped to the primary address register of the respective port address and the Port Con-
trol Register (PxCR), to the corresponding auxiliary register.
There are three different directional ports available:
Port 2
Port 5
Port 4
This, and all other bi-directional ports include a bitwise-programmable Control Register (P2CR),
which enables the individual programming of each port bit as input or output. It also opens up
the possibility of reading the pin condition when in output mode. This is a useful feature for self-
testing and for serial bus applications.
Port 2, however, has an increased drive capability and an additional low resistance
pull-up/-down transistor mask option.
Care should be taken connecting external components to BP20/NTE. During any reset phase,
the BP20/NTE input is driven towards V
pin must not be pulled down (active or passive) to V
resenting a resistor of less than 150 k . This prevents the circuit from unintended switching to
test mode enable through the application circuitry at pin BP20/NTE. Resistors less than 150 k
might lead to an undefined state of the internal test logic thus disabling the application firmware.
To avoid any conflict with the optional internal pull-down transistors, BP20 handles the pull-down
options in a different way than all other ports. BP20 is the only port that switches off the pull-
down transistors during reset.
(Direction)
(Data out)
D
P2DATy
D
P2CRy
S
S
Q
Q
4-bit wide bitwise-programmable I/O port.
4-bit wide bitwise-programmable bi-directional port with optional static
pull-ups and programmable interrupt logic.
4-bit wide bitwise-programmable bi-directional port also provides the I/O
interface to Timer 2, SSI, voltage monitor input and external interrupt input.
(1)
Mask options
DD
by an additional internal strong pull-up transistor. This
(1)
(1)
SS
Pull-up
(1)
(1)
Pull-down
during reset by any external circuitry rep-
V
DD
(1)
(1)
V
DD
BP2y
Static
Pull-up
Static
Pull-down
4708D–4BMCU–09/05