name:         HT9315DV
function:     15-Memory Tone/Pulse Dialers with Volume Switches
package:      SKDIP28,28
manufacturer: Holtek

       +--()--+
    NC | 1  28| NC
    S1 | 2  27| S2
  HDIB | 3  26| HKO
   C1B | 4  25| R4B
   C2B | 5  24| R3B
   C3B | 6  23| R2B
   C4B | 7  22| R1B
   C5B | 8  21| MODE/KT
    X1 | 9  20| DTMF
    X2 |10  19| POB
XMUTEB |11  18| HKSB
   VSS |12  17| VDD
   HFI |13  16| HFO
  DOUT |14  15| CLOCK
       +------+


This pinout came from the Chipdir:
http://www.chipdir.org/