SMC Networks SMC91C95 - Manual (Page 13)

13
DESCRIPTION OF PIN FUNCTIONS
PIN NO. NAME SYMBOL TYPE DESCRIPTION
26 MIDLEN1 O4 Powerdown output to modem controller. This
pin is active (high) when either the PWRDWN
bit (CSR bit 2) is set or the modem is disabled
(not configured).
20 Modem Ring
Input MRINGIN I Ring input from the modem controller.
Toggles when ringing, low when not ringing.
21 nModem
Ring Output
A nMRINGOA O4 Ring output signal. When there is no ringing
on the MRINGIN pin and the modem is not in
Powerdown mode this output is high. During
ringing this signal is the inverse of the
MRINGIN input. When the PWRDWN bit is
set or the function is disabled, this output is
low. This signal is activated about 12 msec
after removing Powerdown.
22 Modem Ring
Output B MRINGOB O4 Ring output signal. When the modem is not in
Powerdown mode (PWRDWN bit is zero and
the function is enabled) this output follows the
value of the MRINGIN input. When entering
Powerdown mode, a rising edge is generated
on the pin. A rising edge is also generated
when exiting Powerdown mode also. Refer to
Figure 2.
14 Speaker
Input SPKRIN I with pullup Speaker Input. This is a digitized (single level)
audio input from the modem controller.
15 Speaker
Output SPKROUT O4 tri-stable
with pullup
Speaker Output. This pin reflects the SPKRIN
pin when enabled by the AUDIO bit (Modem
CSR bit 3). When disabled this pin is tri-
stated.
28 nMPDOUT I Schmitt Used to control Powerdown mode. Tie to a
180K pull-up and a 0.1uF cap to ground.
Tie high when not used. This signal is used
in the RC time constant.
29 MFBK1 O4 with
pullup
Tie to nMPDOUT through a 5.1M resistor.
This signal is used in the RC time constant
in conjuction with the nMPDOUT pin.