PIC18F87K22 Datasheet, PDF (165/548 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Enhanced Flash Microcontrollers with 12-Bit A/D and nanoWatt XLP Technology

PIC18F87K22 FAMILY
12.1.3 OPEN-DRAIN OUTPUTS
The output pins for several peripherals are also
equipped with a configurable, open-drain output option.
This allows the peripherals to communicate with
external digital logic, operating at a higher voltage
level, without the use of level translators.
The open-drain option is implemented on port pins
specifically associated with the data and clock outputs
of the USARTs, the MSSP module (in SPI mode) and
the CCP modules. This option is selectively enabled by
setting the open-drain control bits in the registers
ODCON1, ODCON2 and ODCON3.
When the open-drain option is required, the output pin
must also be tied through an external pull-up resistor
provided by the user to a higher voltage level, up to 5V
(Figure 12-2). When a digital logic high signal is output,
it is pulled up to the higher voltage level.
FIGURE 12-2:
USING THE OPEN-DRAIN
OUTPUT (USART SHOWN
AS EXAMPLE)
3.3V
+5V
PIC18F87K22
VDD
TXX ^3.3V
5V
(at logic ‘1’)
REGISTER 12-2: ODCON1: PERIPHERAL OPEN-DRAIN CONTROL REGISTER 1
R/W-0
R/W-0
R/W-0
U-0
U-0
U-0
U-0
SSP1OD
CCP2OD CCP1OD
—
—
—
—
bit 7
R/W-0
SSP2OD
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
bit 6
bit 5
bit 4-1
bit 0
SSP1OD: MSSP1 Open-Drain Output Enable bit
1 = Open-drain capability enabled
0 = Open-drain capability disabled
CCP2OD: ECCP2 Open-Drain Output Enable bit
1 = Open-drain capability enabled
0 = Open-drain capability disabled
CCP1OD: CCP10 Open-Drain Output Enable bit
1 = Open-drain capability enabled
0 = Open-drain capability disabled
Unimplemented: Read as ‘0’
SSP2OD: MSSP2 Open-Drain Output Enable bit
1 = Open-drain capability enabled
0 = Open-drain capability disabled
 2010 Microchip Technology Inc.
Preliminary
DS39960B-page 165