name:         HT99U410A
function:     Enhanced Cordless Phone Controller
package:      DIP40,40
manufacturer: Holtek

           +--()--+
   PD0(KT) | 1  40| PA7(C8B)
 PD1(DOUT) | 2  39| PA6(C7B)
  PB0(R1B) | 3  38| PA5(C6B)
  PB1(R2B) | 4  37| PA4(C5B)
  PB2(R3B) | 5  36| PA3(C4B)
  PB3(R4B) | 6  35| PA2(C3B)
  PB4(R5B) | 7  34| PA1(C2B)
       PB5 | 8  33| PA0(C1B)
       PB6 | 9  32| PC7
       PB7 |10  31| PC6
 PD2(HKSB) |11  30| PC5
PD3(CLOCK) |12  29| PC4(POB)
 PD4(M/BB) |13  28| PC3(HFO)
  PD5(HFI) |14  27| PC2(XMUTEB)
 PD6(MODE) |15  26| DTMF
       PD7 |16  25| PC1(HDIB)
      ROSC |17  24| PC0(HDO)
        X1 |18  23| VSS
        X2 |19  22| MUSIC
       VDD |20  21| AIN
           +------+


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