PSD813F1 STMICROELECTRONICS [STMicroelectronics], PSD813F1 Datasheet - Page 63

• Manufacturer Part Number: PSD813F1
• Description: Flash In-System Programmable ISP Peripherals For 8-bit MCUs
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Preliminary
The
PSD813F1
Functional
Blocks
(cont.)
9.4.3.3 Drive Select Register
The Drive Select Register configures the pin driver as Open Drain or CMOS for some port
pins, and controls the slew rate for the other port pins. An external pull-up resistor should be
used for pins configured as Open Drain.
A pin can be configured as Open Drain if its corresponding bit in the Drive Select Register is
set to a ‘1’. The default pin drive is CMOS.
Aside: the slew rate is a measurement of the rise and fall times of an output. A higher slew
rate means a faster output response and may create more electrical noise. A pin operates
in a high slew rate when the corresponding bit in the Drive Register is set to ‘1’. The default
rate is slow slew.
Table 27 shows the Drive Register for Ports A, B, C, and D. It summarizes which pins can
be configured as Open Drain outputs and which pins the slew rate can be set for.
NOTE: NA = Not Applicable.
Table 27. Drive Register Pin Assignment
Register
Port A
Port B
Port C
Port D
Drive
Open
Drain
Open
Drain
Open
Drain
Bit 7
NA
Open
Drain
Open
Drain
Open
Drain
Bit 6
NA
Open
Open
Open
Bit 5
Drain
Drain
Drain
NA
Open
Drain
Open
Drain
Open
Drain
Bit 4
NA
Open
Drain
Bit 3
Slew
Rate
Slew
Rate
NA
Open
Drain
Bit 2
Slew
Rate
Slew
Rate
Slew
Rate
Open
Bit 1
Drain
Slew
Slew
Slew
Rate
Rate
Rate
PSD813F1-A
Open
Drain
Bit 0
Slew
Slew
Slew
Rate
Rate
Rate
59