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1.7.3.5 Pull-Up/Pull-Down Inhibit Register (PDINHIBR1, PDINHIBR2, and PDINHIBR3 [1C17h, 1C18h, and
1C19h]
The device allows you to individually enable or disable the internal pull-up and pull-down resistors. You
can individually inhibit the pull-up and pull-down resistors of the I/O pins through the pull-down/up inhibit
registers (PDINHIBRn). There is one pin, TRSTN, that has a pulldown that is permanently enabled and
cannot be disabled.
The pull-down inhibit register 1 (PDINHIBR1) is shown in Figure 1-39 and described in Table 1-49.
Figure 1-39. Pull-Down Inhibit Register 1 (PDINHIBR1) [1C17h]
15 14 13 12 11 10 9 8
Reserved S15PD S14PD S13PD S12PD S11PD S10PD
R-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
7 6 5 4 3 2 1 0
Reserved S05PD S04PD S03PD S02PD S01PD S00PD
R-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 1-49. Pull-Down Inhibit Register 1 (PDINHIBR1) Field Descriptions
Bit Field Value Description
15-14 Reserved 0 Reserved.
13 S15PD Serial port 1 pin 5 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
12 S14PD Serial port 1 pin 4 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
11 S13PD Serial port 1 pin 3 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
10 S12PD Serial port 1 pin 2 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
9 S11PD Serial port 1 pin 1 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
8 S10PD Serial port 1 pin 0 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
7-6 Reserved 0 Reserved.
5 S05PD Serial port 0 pin 5 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
4 S04PD Serial port 0 pin 4 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
3 S03PD Serial port 0 pin 3 pull-down inhibit bit. Setting this bit to 1 disables the pin's internal pull-down.
0 Pin pull-down is enabled.
1 Pin pull-down is disabled.
67
SPRUFX5A–October 2010–Revised November 2010 System Control
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