PSD935G2-90U STMicroelectronics, PSD935G2-90U Datasheet - Page 52

• Manufacturer Part Number: PSD935G2-90U
• Manufacturer: STMicroelectronics

Specifications of PSD935G2-90U

• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Package Type: TQFP
• Mounting: Surface Mount
• Pin Count: 80
• Lead Free Status / RoHS Status: Compliant

PSD935G2
The
PSD935G2
Functional
Blocks
(cont.)
Table 23. Port Data Registers
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 22 shows the Drive Register for Ports A, B, C, D, E and G. It summarizes which
pins can be configured as Open Drain outputs and which pins the slew rate can be set for.
Port F always has CMOS drive.
Table 22. Drive Register Pin Assignment
9.4.4 Port Data Registers
The Port Data Registers, shown in Table 23, are used by the microcontroller to write data
to or read data from the ports. Table 23 shows the register name, the ports having each
register type, and microcontroller access for each register type. The registers are
described below.
9.4.4.1 Data In
Port pins are connected directly to the Data In buffer. In MCU I/O input mode, the pin input
is read through the Data In buffer.
9.4.4.2 Data Out Register
Stores output data written by the MCU in the MCU I/O output mode. The contents of the
Register are driven out to the pins if the Direction Register or the output enable
product term is set to “1”. The contents of the register can also be read back by the
microcontroller.
Register
Port A
Port B
Port C
Port D
Port E
Port G
Drive
Register Name
Data Out
Data In
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Bit 7
Slew
Rate
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 6
Slew
Rate
A,B,C,D,E,F,G
A,B,C,D,E,F,G
Port
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 5
Slew
Rate
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Bit 4
Slew
Rate
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 3
Slew
Rate
Read – input on pin
MCU Access
PSD9XX Family
Write/Read
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 2
Slew
Rate
Open
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Drain
Bit 1
Slew
Rate
Open
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Drain
Bit 0
Slew
Rate
51