c8051f410 Silicon Laboratories, c8051f410 Datasheet - Page 152

• Manufacturer Part Number: c8051f410
• Description: 2.0 V, 32/16 Kb Flash, Smartclock, 12-bit Adc
• Manufacturer: Silicon Laboratories

C8051F410/1/2/3
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMD-
OUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings. When the WEAKPUD bit in XBR1 is ‘0’, a weak pullup is enabled for all Port I/O con-
figured as open-drain. WEAKPUD does not affect the push-pull Port I/O. Furthermore, the weak pullup is
turned off on an output that is driving a ‘0’ and for pins configured for analog input mode to avoid unneces-
sary power dissipation.
Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions
required by the design. Setting the XBARE bit in XBR1 to ‘1’ enables the Crossbar. Until the Crossbar is
enabled, the external pins remain as standard Port I/O (in input mode), regardless of the XBRn Register
settings. For given XBRn Register settings, one can determine the I/O pin-out using the Priority Decode
Table.
The Crossbar must be enabled to use Port pins as standard Port I/O in output mode. Port output drivers
are disabled while the Crossbar is disabled.
152
V
Cell
I/O
V
IO
DD
Figure 18.5. Port 0 Input Overdrive Current Range
P0.x
pin
I
Vtest
+
-
V
test
High-Impedance Mode
P0ODEN.x = 0
P0ODEN.x = 1
Rev. 1.0
Normal Mode
I
I
Vtest
Vtest
(µA)
(µA)
-150
-10
-10
10
0
0
V
IO
V
-0.2
IO
V
V
IO
IO
+0.7
+0.2
V
V
test
test
(V)
(V)