EM6520 Datasheet, PDF (14/55 Pages) EM Microelectronic - MARIN SA – MFP version of EM6620 Ultra Low Power Microcontroller 4x8 LCD Driver

EM6520
6.2 Port A
The EM6520 has one four bit general purpose CMOS input port. The port A input can be read at any time, pull-
up or pull-down resistors can be chosen by metal mask (ROM version only). All selections concerning port A are
bit-wise executable. I.e. Pull-up on PA[2], pull-down on PA[0], positive IRQ edge on PA[0] but negative on PA[1],
etc.
In sleep mode the port A inputs are continuously monitored to match the input reset condition which will
immediately wake up the EM6520. The pull-up or pull-down resistors remain active as defined in the option
register.
Figure 10. Input Port A Configuration
VBAT
(VDD)
NoDebIntPA[n]=1
Mask opt
MPAPU[n]
PA[n]terminal
Debouncer
Mask opt
MPAPD[n]
Ck[8] Ck[11] or Ck[14]
IntEdgPA[n]=0
PA3 for the
Millisecond
Counter
IRQPA[3:0]
PA0, PA3
for 10-bit
Counter
µP TestVar
DB[3:0]
VSS
NoPull[n]
6.2.1 IRQ on Port A
For interrupt request generation (IRQ) one can choose direct or debounced input and positive or negative edge
IRQ triggering. With the debouncer selected ( OPtDebIntPA ) the input must be stable for two rising edges of
the selected debouncer clock (RegPresc). This means a worst case of 16ms(default) or 2ms (0.25ms by metal
mask) with a system clock of 32kHz.
Either a positive or a negative edge on the port A inputs - after debouncer or not - can generate an interrupt
request. This selection is done in the option register OPTIntEdgPA.
All four bits of port A can provide an IRQ, each pin with its own interrupt mask bit in the RegIRQMask1 register.
When an IRQ occurs, inspection of the RegIRQ1, RegIRQ2 and RegIRQ3 registers allow the interrupt to be
identified and treated.
At power on or after any reset the RegIRQMask1 is set to 0, thus disabling any input interrupt. A new interrupt is
only stored with the next active edge after the corresponding interrupt mask is cleared. See also the interrupt
chapter 9.
It is recommended to mask the port A IRQ’s while one changes the selected IRQ edge. Else one may generate
a IRQ (Software IRQ). I.e. PA[0] on ‘0’ then changing from positive to negative edge selection on PA[0] will
immediately trigger an IRQPA[0] if the IRQ was not masked.
EM Microelectronic-Marin SA CH-2074 Marin, Switzerland, Tel. [phone], Fax. [phone]
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© EM Microelectonic-Marin SA , 12/98 Rev. A/246
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