em6521 EM Microelectronic, em6521 Datasheet - Page 16

• Manufacturer Part Number: em6521
• Description: Mfp Version Of Em6621 Ultra Low Power Microcontroller With 4x20 Lcd Driver
• Manufacturer: EM Microelectronic

6.2.2 Pull-up or Pull-down
Each of the input port terminals PA[3:0] has a resistor integrated which can be used either as pull-up or pull-
down resistor, depending on the selected metal mask options( ROM version only). See the port A metal mask
chapter for details. The pull resistor can be inhibited using the NoPullPA[n] bits in the register OptNoPullPA.
Table 6.2.1. Pull-up or Pull-down Resistor on Port A Inputs
* only pull-up or pull-down may be chosen on any port A terminal (one choice is excluding the other)
6.2.3 Software Test Variables
The port A terminals PA[2:0] are also used as input conditions for conditional software branches. Independent
of the OPTDebIntPA and the OPTIntEdgPA. These CPU inputs always have a debouncer.
- Debounced PA[0] is connected to CPU TestVar1.
- Debounced PA[1] is connected to CPU TestVar2.
- Debounced PA[2] is connected to CPU TestVar3.
6.2.4 Port A for 10-Bit Counter and MSC
The PA[0] and PA[3] inputs can be used as the clock input terminal for the 10 bit counter in "event count"
mode. As for the IRQ generation one can choose debouncer or direct input with the register OPTDebIntPA and
non-inverted or inverted input with the register OPTIntEdgPA. Debouncer input is always recommended.
Pad input PA[3] is also used as start/stop control for the millisecond counter. This control signal is derived from
PA[3], it is independent of the port A debouncer and edge selection. Refer also to
6.3 Port A Registers
Table 6.3.1 Register RegPA
Copyright © 2005, EM Microelectronic-Marin SA
Option mask
MPAPU[n]
Bit
3
2
1
0
pull-up
* Direct read on port A terminals
yes
yes
yes
no
no
no
R
PAData[3]
PAData[2]
PAData[1]
PAData[0]
Name
Option mask
MPAPD[n]
pull-down
yes
yes
yes
no
no
no
Reset
-
-
-
-
NoPullPA[n]
R/W
value
R*
R*
R*
R*
x
0
1
0
1
x
16
no pull-up , no pull-down
no pull-up, no pull-down
no pull-up, no pull-down
no pull-up, pull-down
pull-up, no pull-down
not allowed*
PA[3] input status
PA[2] input status
PA[1] input status
PA[0] input status
Action
Description
F igure 10.
1 1 4 H
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EM6521
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