45181 Parallax Inc, 45181 Datasheet - Page 89
45181
Manufacturer Part Number
45181
Description
SX TECH TOOL KIT NO POWER
Manufacturer
Parallax Inc
Series
SXr
Type
Microcontrollerr
Datasheet
1.45180.pdf
(184 pages)
Specifications of 45181
Contents
SX Book, SX Key, SX Tech Board, Samples, Resonators, Cable and Manual
Product
Microcontroller Basic Stamps
Operating Supply Voltage
5 V
For Use With/related Products
SX MCUs
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
- Current page: 89 of 184
- Download datasheet (2Mb)
10.2.2 Pull-Up Resistors
Every I/O pin has optional internal pull-up resisters that can be configured by writing to the
appropriate pull-up register (PLP_A, PLP_B, PLP_C, PLP_D and PLP_E). By configuring pull-up
resisters on input pins, the SX chip can be connected directly to open/drain circuitry without the need
for external pull-up resisters. The internal pull-up resisters are disabled by default. Pull-up resisters can
be activated for all pins, regardless of pin direction but really matter only when the associated pin is set
to input mode.
To configure the I/O pins to have internal pull-up resisters:
The following code snippet demonstrates this:
1) Set the MODE register to $0E (the value for pull-up register configuration).
2) Use the port configuration instruction to set the individual pull-up state of each I/O pin within
3) Set I/O pin directions as necessary.
each port. A high bit (1) disables the pull-up for the corresponding pin and a low bit (0) enables the
pull-up resister for a pin.
; Set output pins low
;
MOV
MOV
MOV
; Pull-Up Resistor Configuration
;
MODE $0E
MOV
MOV
MOV
MODE $0F
MOV
MOV
MOV
ra, #%0000
rb, #%00000000 ; Port B bits 0-7 low
rc, #%00000000 ; Port C bits 0-7 low
!ra,#%0000
!rb,#%11110000 ; Port B bits 4-7 normal, bits 0-3 pull-ups
!rc,#%00001111 ; Port C bits 4-7 pull-ups, bits 0-3 normal
!ra,#%1111
!rb,#%00001111 ; Port B bits 4-7 to output, bits 0-3 input
!rc,#%11110000 ; Port C bits 4-7 to input, bits 0-3 output
; Port A bits 0-3 low
; Set Mode for Pull-Up Resistor configuration
; Port A bits 0-3 to pull-ups
; Set Mode to allow Direction configuration
; Port A bits 0-3 to input
10 SX Special Features and Coding Tips
SX-Key/Blitz Development System Manual 2.0 Parallax, Inc. Page 89
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