EM6821 datasheet(39/68 Pages) EMMICRO

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EM6821

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• CPU controlled Start and PA[3] controlled Stop.

In this mode setting the bit RunEn=1 while PA3/uP=0 while immediately start the counting action. Afterwards

one needs to prepare for the stop by PA[3]. Therefore the PA[3] start condition must first be fulfilled. This is in

dT mode a rising edge on the PA3internal signal (PA3internal, refer to Figure 27). In MSC mode the start

condition is a positive pulse on PA3internal signal. The creation of this edge or pulse is done per software by

manipulating the PA3Edge selection. See Figure 29 for details. Afterwards one can change to PA3 controlled

stop mode (PA3/uP=1) where the next positive edge on PA3internal will stop the Counter. In dT mode the

RunEn/stop bit will be cleared with the PA3 stop condition where as in MSC mode MSC mode the RunEn is

not cleared.

• Pulse-width measurement of PA[3] Input Signals.

In this mode the bit dT/MSC=1 and PA3/uP=1. Setting

RunEn/stop=1 enables the operation. The first positive

edge on PA3Internal signal will start the counter, the

following negative edge will stop the counter end set bit

RunEn/Stop to 0 . PA3internal signal is a copy of the PA[3]

terminal

status

PA3Edge=1.

with

PA3Edge=0

PA3Internal has the inverted

PA[3]

value.

See also

Figure 27 and Figure 30.

• Port A PA[3] controlled Start and Stop Mode.

In this mode the bit dT/MSC=0 and PA3/uP=1. Setting

RunEn/stop=1 enables the operation. The first positive

edge on PA3Internal signal will start the counter , the

second edge will stop the counter, the third one will restart,

etc, . PA3internal signal is a copy of the PA[3] terminal

status if PA3Edge=1. With PA3Edge=0 PA3Internal has

the inverted PA[3] value. See also Figure 27 and Figure 30.

Figure 29. CPU controlled Start PA[3] controlled Stop

C ount i n g

Se t

I n it ia l

V a l ues

St o p

St a r t

PA 3

St a r t

µP

dT / M S C = 1 , S t op on P A [ 3 ] R i s i ng E dge

CP U W r i t e

P A 3E dge

P A 3/ uP

R unE n/ S t op

P A 3I nt er nal

C ount

PA [ 3 ]

Se t

I n it ia l

V a l ues

C ount i n g

St o p

St a r t

PA 3

St a r t

µP

dT / M S C = 1 , S t op on P A [ 3 ] F a l l i ng E dge

CP U W r i t e

P A 3E dge

P A 3/ uP

R unE n/ S t op

P A 3I nt er nal

C ount

PA [ 3 ]

C ount i n g

Se t

I n it ia l

V a l ues

St o p

St a r t

PA 3

St a r t

µP

dT / M S C = 0 , S t op on P A [ 3] R i s i ng E dge

CP U W r i t e

P A 3E dge

P A 3/ uP

R unE n/ S t op

P A 3I nt er nal

C ount

PA [ 3 ]

C ount i n g

Se t

I n it ia l

V a l ues

St o p

St a r t

PA 3

St a r t

µP

dT / M S C = 0 , S t op on P A [ 3 ] F a l l i ng E dge

CP U W r i t e

P A 3E dge

P A 3/ uP

R unE n/ S t op

P A 3I nt er nal

C ount

PA [ 3 ]

Figure 30. dT/MSC behavior

restart

stop

start

stop

start

Counter

RunEn

Counting

PA3 internal

Period

m easurem ent

dT/MSC=0,

PA3/up=1

Pulse-width

Measurem ent

dT/MSC, PA3/up=1

Counter

RunEn

PA3 internal

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