View source for 5.8051 Timer programming ← 5.8051 Timer programming

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In this tutorial we will see 8051 timers. We will use the 8051 timers to generate a precise delay of 1 sec.
=8051 timers/counters= 
The 8051 has 2 timers/counters. 
*They can be used to generate precise timing, i.e., we can measure time between events. The unit is then called '''timer'''.
*It can also be used to count external events, known as '''counter'''.
*'''Timer 1''' is also used for generating baud rate in serial communication, which we will discuss in the next tutorial<br />
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==Timer Counter Operation==
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The Timer 0 is a 16 bit registers as shown. This can be accessed as 2 eight bit registers '''TL0 and TL1'''. Same applies to Timer 1.
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[[File:Basic Timer.jpeg|thumbnail|600xpx|fig:Basic Timer]]
[[File:Mode_0.jpeg|thumbnail|600xpx|fig:Mode 0]]
[[File:Mode_1.jpeg|thumbnail|600xpx|fig:Mode 1]]
[[File:Mode_2.jpeg|thumbnail|600xpx|fig:Mode 2]]



{| class="wikitable" style="text-align:center;background-color:#87A96B;margin: 1em auto 1em auto;"
|+ Table. 1: Timer Register
|-
!colspan = '16'|T0
|-
|colspan='8'|TH0||colspan='8'|TL0
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|D15||D14||D13||D12||D11||D10||D9||D8||D7||D6||D5||D4||D3||D2||D1||D0
|}

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The '''TMOD''' Register specifies the operational mode of the two timers. The higher nibble is used for Timer 1 and Lower for the timer 0 as shown below.
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{| class="wikitable floatright" style="text-align:center;background-color:#87A96B;"
|+ Table 3. Timer Modes
|-
!M1||M0||Operation
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|0||0||13 bit Timer
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|0||1||16 bit Timer
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|1||0||8 bit Auto Reload
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|1||1||Split Mode
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{| class="wikitable" style="text-align:center;background-color:#87A96B;"
|+ Table 2. TMOD Register
|-
!colspan = '8'|TMOD
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|D7||D6||D5||D4||D3||D2||D1||D0
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|Gate||C/T||M1||M0||Gate||C/T||M1||M0
|-
!colspan="4"|Timer1||colspan="4"|Timer 0
|}