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

MRINGIN

I

Ring input from the modem controller.

 

Input

 

 

Toggles when ringing, low when not ringing.

 

 

 

 

 

21

nModem

nMRINGOA

O4

Ring output signal. When there is no ringing

 

Ring Output

 

 

on the MRINGIN pin and the modem is not in

 

A

 

 

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

MRINGOB

O4

Ring output signal. When the modem is not in

 

Output B

 

 

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

SPKRIN

I with pullup

Speaker Input. This is a digitized (single level)

 

Input

 

 

audio input from the modem controller.

 

 

 

 

 

15

Speaker

SPKROUT

O4 tri-stable

Speaker Output. This pin reflects the SPKRIN

 

Output

 

with pullup

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

Tie to nMPDOUT through a 5.1M resistor.

 

 

 

pullup

This signal is used in the RC time constant

 

 

 

 

in conjuction with the nMPDOUT pin.

 

 

 

 

 

 

 

 

13

 

Page 13
Image 13
SMC Networks SMC91C95 Pin is active high when either the Pwrdwn, Modem Ring, Ring input from the modem controller, Speaker