How does a 74(ALS/LS/S)168 work?

Hi all,
I am trying to make a countdown timer for my GCSE project- one of the IC's the school has to hand is the 74(ALS/LS/S)168. They did have a book that explained how it worked, but someone has gone and lost it (not me!). It is described as a Synch decade u/d counter and has 16 pins:

1 =Up/Down
2 =Clock
3 =Data Input A
4 =Data Input B
5 =Data Input C
6 =Data Input D
7 =Enable P
8 =GND
9 =LOAD
10=Enable T
11=Output Qa
12=Output Qb
13=Output Qc
14=Output Qd
15=Carry output
16=Vcc

Thanks in advance
Eraser

Maybe this help.If You need the complete d'sheet, PM me with mail address.