This is a complete project Jure sent me with PCB design. It can be compiled with the BASCOM-8051 info since Jure used the AT89C2051 with 2KB of code.

Here is the comment from Jure:

Here is the description of the Timer:

S.E. Timer can countdown from 1-99 seconds, 1-99 minutes or 1-99 hours.

Timer has 4+1 press buttons, UP, DOWN, MODE, START + RESET

UP, DOWN set time that we want to count down, MODE selects the unit (sec., min. or hours) that we want to count down. Once we set time and set MODE, we can start countdown sequence. After countdown the relay turns on. To restart Timer, we must press RESET button.

In the countdown mode no buttons except RESET are active.

Download source code in .BAS file
Download PCB file #1
Download PCB file #2

And here is the BASCOM-8051 code:

' S.E. Timer, improved version
' author Jure Mikeln, December 2000
' S.E. Timer can countdown from 1-99 seconds
' 1-99 minutes or 1-99 hours
' Timer has 4+1 press buttons, UP, DOWN, MODE, START + RESET
' UP, DOWN set time that we want to count down
' MODE selects the unit (sec., min. or hours) that we want to
'  count down. Once we set time, set MODE, we can start countdown
' sequence. After countdown the relay turns on. To restart Timer,
' we must press RESET button.
' In the countdown mode no buttons except RESET are active.
' PCBs for Timer are available from: stik@svet-el.si
' or www.svet-el.si/english

Dim Clock As Byte , Stevec As Byte , Segmenti As Byte , X As Byte , P15 As Bit , P16 As Bit , P17 As Bit
Dim Clock12 As Word , Stevec1 As Bit , Stevec2 As Byte , Mux As Byte , Prikaz As Bit
Dim T1 As Bit , T2 As Bit , T3 As Bit
Dim Clock1 As Byte , Mod1 As Byte
Dim Izracun As Bit , Pomozna_v As Byte , Enice As Byte , Desetice As Byte , Minute As Word , Ure As Word

' SEGMENTS ARE AT P1.1 to P1.7
' P1.6 flashes with respect Timer MODE
' Mod=1=>sec =>P1.6 flashes quickly, Mod=2=>min =>P1.6 flashes slowly,
' Mod=3=>ure =>P1.6 glows constantly

Config Timer0 = Timer , Gate = Internal , Mode = 2
Config Debounce = 10
'Gate = Internal
'Mode = 2  8 bit auto reaload

Enable Interrupts
Enable Timer0
Load Timer0 , 250
Start Timer0

'initial settings

Clock = 0
Stevec = 0
T1 = P3.0 ' UP button
T2 = P3.2 ' DOWN button
T3 = P3.1 ' MODE button
'P3.0 and P3.1 together ' START button, see schematics
P16 = 1
P15 = 0
Mod1 = 1
P3.7 = 0
Reset Segmenti
Minute = 0
Clock12 = 0
Ure = 0
On Timer0 Timer_0_int

'------------------------------------------------------------------
'Main program

Do

T3 = P3.1
T1 = P3.0
T2 = P3.2

If Mod1 = 1 Then
 P1.6 = P15
End If 'P1.6 flashes quickly (seconds)

If Mod1 = 2 Then
 P1.6 = P16 'P1.6 flashes slowly (minutes)
End If

If Mod1 = 3 Then
 P1.6 = 0 'P1.6 glows constantly (hours)
End If

Gosub Tipke
Gosub Izracun1

Loop
End
'------------------------------------------------------------------
'Interrupt routine

Timer_0_int:
Incr Clock12
If Clock12 > 4000 Then
 Clock12 = 0
 P16 = Not P16 'one second pulse
 P17 = Not P17  'seconds indication
End If

Incr Clock
If Clock > 19 Then 'each 5 mS change of MUX-a
 Clock = 0
 Incr Mux
 If Mux > 3 Then
 Mux = 0
 End If
 Prikaz = 1
 Incr Clock1
 If Clock1 > 29 Then
 Clock1 = 0
 P15 = Not P15 'LED flashes every 150mSec.
 End If
End If
Return
'------------------------------------------------------------------
'Press buttons routine

Tipke:
If Mux > 2 Then 'this prevents turning LED display off when buttons are pressed
Debounce T1 , 0 , Stevec1 , Sub 'UP
Debounce T2 , 0 , Stevec , Sub 'DOWN
Debounce T3 , 0 , Mod , Sub 'MODE
End If
Return
'------------------------------------------------------------------
'Decrement variable Stevec

Stevec:
If Stevec > 0 Then
 Decr Stevec
 If Stevec = 255 Then
 Stevec = 99
 End If
End If
Return
'------------------------------------------------------------------
'Increment variable Stevec

Stevec1:
If T3 = 0 Then 'start countdown
 Gosub Odstej1 'go to sub for decrementing
 Return
End If

Incr Stevec
If Stevec > 99 Then 'prevent Stevec to increment over 99
 Stevec = 0

End If
Return
'------------------------------------------------------------------
'MODE select routine
'Mod1=1 seconds, Mod1=2 minutes, Mod1=3 hours

Mod:
Incr Mod1

If Mod1 > 3 Then
 Mod1 = 1
End If
Return
'------------------------------------------------------------------
'Routine that calculates tenths & units

Izracun1:
 Desetice = Stevec / 10
 Pomozna_v = Desetice * 10
 Enice = Stevec - Pomozna_v

If Prikaz = 1 Then
 Prikaz = 0
 P3.4 = 1
 P3.5 = 1 'disable display
 'disable display
 If Mux = 0 Then
 Pomozna_v = Enice 'show units
 Gosub Prikaz1 'gosub for displaying
 P3.5 = 0 'enable transistor for units
 End If

 If Mux = 1 Then
 Pomozna_v = Desetice 'show tenths
 Gosub Prikaz1 'gosub for displaying
 P3.4 = 0 'enable transistor for tenths
 End If
End If
Return
'------------------------------------------------------------------
'Displaying routine

Prikaz1:
Restore Tabela

For X = 0 To 9
 Read Segmenti
 If X = Pomozna_v Then 'if X = value to display
 P1 = Segmenti 'then set this value to Port1
 Exit For 'and exit FOR loop
 End If
 Next
Return

'---- data for LED display ------
Tabela:
Data 96 , 249 , 196 , 208 , 89 , 82 , 66 , 248 , 64 , 80
'------------------------------------------------------------------
'Routine that decrements preset time

Odstej1:
Clock12 = 0 'reset timer variable
P16 = 1
Do
If Stevec > 0 Then 'condition that prevents decr. below zero
 Gosub Ure_sub 'gosub hours
 Gosub Minute_sub 'gosub minutes
 Gosub Sekunde_sub 'gosub seconds
 Else
 Exit Do 'it does not decrement if Stevec=0
End If
Loop
Return
'------------------------------------------------------------------
'Routine for minutes decrement

Minute_sub:
If Mod1 = 2 Then 'check if Timer is in minutes MODE
 Do
 P1.6 = P17 'signalization that it's minutes
 Min1:
 If P16 = 0 Then 'wait until P16 changes it's state (every second)
 P16 = Not P16
 Incr Minute 'incr Minutes variable
 If Minute > 59 Then 'if minutes > 59 then
 Minute = 0
 Decr Stevec 'decr variable Stevec every 60 sec
 If Stevec = 1 Then
 Stevec = 60
 Mod1 = 1
 Return
 End If
 If Stevec = 0 Then
 P3.7 = 1 'turn on relay
 P3.4 = 0 'both displays are on
 P3.5 = 0
 P1 = 96 'display "0" on display
 Stop
 End If
 End If
 End If
 Gosub Izracun1 'display value of Stevec variable
 Loop
End If
Return
'------------------------------------------------------------------
'Routine that decrements preset hours

Ure_sub:
If Mod1 = 3 Then 'check if Timer is in hours MODE
 Do
 P1.6 = 0 'signalization of Hours MODE
 If P16 = 0 Then 'wait until P16 changes it's state (every second)
 P16 = Not P16
 Incr Ure
 If Ure > 3599 Then
 Ure = 0
 Decr Stevec 'decrement Stevec variable every 3600 seconds
 If Stevec = 1 Then 'when Stevec=1,
 Stevec = 60 'Set Stevec=60 and decrement minutes
 Mod1 = 2 'Set Mod1 to minutes MODE
 Return
 End If
 If Stevec = 0 Then
 P3.7 = 1 'turn on relay
 P3.4 = 0 'both displays are on
 P3.5 = 0
 P1 = 96 'display number "0"
 Stop
 End If
 End If
 End If
 Gosub Izracun1 'display value of Stevec variable
 Loop
End If
Return
'------------------------------------------------------------------
'Routine for Seconds decrementing

Sekunde_sub:
Do
If Mod1 = 1 Then
 If P16 = 0 Then 'wait until P16 changes it's state (every second)
 P16 = Not P16
 Decr Stevec 'Decrement variable Stevec for 1
 If Stevec = 0 Then
 P3.7 = 1 'turn on relay
 P3.4 = 0 'both displays are on
 P3.5 = 0
 P1 = 96 'display number "0"
 Stop
 End If
 End If
End If
Gosub Izracun1 ''display value of Stevec variable
Loop
Return
'------------------------------------------------------------------