EM6520 EM Microelectronic, EM6520 Datasheet - Page 15

• Manufacturer Part Number: EM6520
• Description: MFP version of EM6620 Ultra Low Power Microcontroller 4x8 LCD Driver
• Manufacturer: EM Microelectronic

6.2.2 Pull-up/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). The pull resistor can be
inhibited using the NoPullPA[n] bits in the register OptNoPullPA. Refer also to chapter 16.1.1 .
Table 6.2.1. Pull-up or Pull-down Resistor on Port A select
* only pull-up or pull-down may be chosen on any port A terminal (one choice is excluding the other)
Any port A input must never be left open (high impedance state, not connected, etc. ) unless the internal pull
resistor is in place (mask option) and switched on (register selection). Any open input may draw a significant
cross current which adds to the total chip consumption.
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 are always debounced and non-inverted.
- 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 Figure 10.
6.3 Port A registers
Table 6.3.1 Register RegPA
Copyright  2002, 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
Name
PA[3]
PA[2]
PA[1]
PA[0]
Option mask
MPAPD[n]
pull-down
yes
yes
yes
no
no
no
Reset
-
-
-
-
NoPullPA[n]
R/W
value
R*
R*
R*
R*
0
1
0
1
x
x
15
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
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EM6520
with
n=0…3
03/02 REV. D/449