EM78808
8-bit Micro-controller
OPOUT bit
1
Schmitt trigger input
0
2.5V
1.2V
5V
Fig.23 Transition curve of Schmitt trigger
Bit 1 (OPEN) : Power control for OP block
0/1 ꢂdisable OP/enable OP
Bit 2~Bit 3 (P5S1~P5S2) : PORT5 switch
P5S2
0 or 1
0
1
0
P5S1
OPEN PORT55
PORT56
PORT56
OP+
OP+
OP+
PORT57
PORT57 Normal PORT5 IO
OPO
OPO
OPO
OPO
Status
0
0
0
1
1
1
0
1
1
1
1
0
PORT55
OP-
OP-
OP-
OP-
Power off OP block
Amp
(unused)
Amp and Schmitt
1
OP+
EST
0 or 1
STGT
PORT57 DTMF receiver IO
<Note> In the status items, “Amp” means OP block works as amplifier only. Schmitt trigger is output disable. It
can be a general OP amplifier.
In the status items, “Amp and Schmitt” means OP block works as amplifier and Schmitt trigger is output enable.
The output of amplifier will be fed to the input of Schmitt trigger. It can be an energy detector.
PORT57
MUX
2
EST
PORT56
+
MUX
OPOUT
OP+
-
2
P5S2,P5S1
STGT
PORT55
MUX
OP-
OPEN
2
P5S2,P5S1
Fig.24 OP structure
External reference signal
The analog signal that is presented at Cin- compares to the signal at Cin+, and the digital output of the
______________________________________________________________________________________________________________________________________________________
* This specification is subject to change without notice.
8/1/2004 (V3.1)
41
ELAN [ ELAN MICROELECTRONICS CORP ]
