ATAM862-8 Datasheet, PDF (34/107 Pages) ATMEL Corporation – Microcontroller with UHF ASK/FSK Transmitter

Figure 28. Bi-directional Port 1
I/O Bus
OUT
IN
Master reset
(Data out)
DQ
P1DATy
R
Reset
(Direction)
SQ
R NQ
V _DD
*
* Switched
pull-up
*
*) Configurable
V _DD
*
Switched
pull-down
Static
pull-up
BP1y
Static
pull-down
Bi-directional Port 2
As all other bi-directional ports, this port includes a bitwise programmable Control Reg-
ister (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/pull-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_DD by an additional internal strong pull-up
transistor. This pin must not be pulled down (active or passive) to V_SS during reset by
any external circuitry representing a resistor of less than 150 kΩ. This prevents the cir-
cuit from unintended switching to test mode enable through the application circuitry at
pin BP20/NTE. Resistors less than 150 kΩ might lead to an undefined state of the inter-
nal 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.
Figure 29. Bi-directional Port 2
I/O Bus
I/O Bus
(Data out)
DQ
P2DATy
S
Master reset
Switched
pull-up
*
V _DD
Static
Pull-up
*
*
BP2y
*
V _DD
I/O Bus
D ^SQ
P2CRy
(Direction)
* Configurable
*
* ^Static
Pull-down
Switched
pull-down
34 ATAM862-8
4590E–4BMCU–09/04