HARDWAREDESCRIPTIONOF THE 8051,8052 AND 80C51
CIT. o
.,
PINJ*”
‘ROL~[ M
INTERRUPT
270252-10
Figure9.Timer/Counter1Mode 2: 8-Bit Auto-Reload
EI--EI-’’”SC”SC
11121~’~
/t
I
.PIN~fi=l 1
‘
—
INTERRUPT
CONTROL
1/121“’~
Id’
~
_ INTERRUPT
I CONTROL
TR1~
270252-11
Figure 10. Timer/Counter OMode 3:Two 6-Bit Countere
Timer2
Timer 2 is a 16-bitTimer/Counter which is present
only in the 8052.Like TimersOand 1,it can operate
eitheras a timeror as an eventcounter.Thisis selected
by bit Cm in the SpecialFunctionRegisterT2C0N
(Figure 11).It haa three operatingmodes:“capture,”
“autdoad”
and “baud rate generator,” which are se-
lectedbybitsinT2CONasshowninTable2.
Table 2. Timer 2 Operating Modea
IRCLK + TCLKlCPI~lTR21
Mode
o
0
1 16-bitAuto-Reload
o
1
1 16-bitCapture
1
x 1 Baud Rate Generator
3-12
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