PSD4235G2V-10U STMICROELECTRONICS [STMicroelectronics], PSD4235G2V-10U Datasheet - Page 64

• Manufacturer Part Number: PSD4235G2V-10U
• Description: Flash In-System Programmable (ISP) Peripherals for 16-bit MCUs
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

PSD4256G6V
Direction Register
The Direction Register controls the direction of
data flow in the I/O Ports. Any bit set to 1 in the Di-
rection Register causes the corresponding pin to
be an output, and any bit set to 0 causes it to be
an input. The default mode for all port pins is input.
Figure 28, page 62 and Figure 30, page 67 show
the Port Architecture diagrams for Ports A/B/C and
E/F/G, respectively. The direction of data flow for
Ports A, B, C and F are controlled not only by the
direction register, but also by the output enable
product term from the PLD AND Array. If the out-
put enable product term is not active, the Direction
Register has sole control of a given pin’s direction.
An example of a configuration for a Port with the
three least significant bits set to output and the re-
mainder set to input is shown in Table 45. Since
Port D only contains four pins, the Direction Reg-
ister for Port D has only the four least significant
bits active.
Drive Select Register
The Drive Select Register configures the pin driver
as Open Drain or CMOS. An external pull-up resis-
tor should be used for pins configured as Open
Drain.
A pin can be configured as Open Drain if its corre-
sponding bit in the Drive Select Register is set to a
1. The default pin drive is CMOS.
Table 46. Drive Register Pin Assignment
Note: 1. NA = Not Applicable.
64/100
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
Port A
Port B
Port D
Port E
Port G
Register
Drive
Open
Open
Open
Open
Drain
Drain
NA
Drain
Drain
Bit 7
(1)
Open
Open
Open
Open
Drain
Drain
NA
Drain
Drain
Bit 6
(1)
Open
Drain
Open
Drain
NA
Open
Drain
Open
Drain
Bit 5
(1)
Open
Open
Open
Open
Drain
Drain
NA
Drain
Drain
Bit 4
(1)
Table 46 shows the Drive Register for Ports A, B,
D, E and G. It summarizes which pins can be con-
figured as Open Drain outputs.
Table 43. Port Pin Direction Control, Output
Enable P.T. Not Defined
Table 44. Port Pin Direction Control, Output
Enable P.T. Defined
Table 45. Port Direction Assignment Example
Bit 7
Direction Register Bit
0
Register Bit
Direction
Open
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Drain
Bit 3
Bit 6
0
0
1
1
0
0
1
Bit 5
0
Output Enable
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 2
Bit 4
0
P.T.
0
1
0
1
Bit 3
0
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Open
Drain
Bit 1
Port Pin Mode
Bit 2
1
Output
Port Pin Mode
Input
Bit 1
Output
Output
Output
Input
1
Open
Open
Open
Open
Open
Drain
Drain
Drain
Drain
Drain
Bit 0
Bit 0
1