45111 Parallax Inc, 45111 Datasheet - Page 89

• Manufacturer Part Number: 45111
• Description: MANUAL FOR SX-KEY/BLITZ VER. 2.0
• Manufacturer: Parallax Inc

Specifications of 45111

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Parallax microcontroller
• For Use With: 70002PAR - GUIDE PROG THE SX MICRO -DAUBACH
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

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