C8051F50x-F51x
CKCON
TMOD
IT01CF
G C T T G C T T
I I I I I I I I
N N N N N N N N
T T T T T T S S
3 3 2 2 1 0 C C
M M M M M M A A
A
/
1
1 A
/
0
0
T T M M T T M M
1
1 1 1 0 0 0 0
E 1
1
1
0 E 0
0
1
0
P S S S P S S S
H L H L
1 0
L
L
2
L
1
L
0
L
L
2
L
1
L
0
Pre-scaled Clock
SYSCLK
0
1
0
1
T0
TF1
TR1
TF0
TR0
IE1
TCLK
TL0
(8 bits)
Interrupt
TR0
IT1
IE0
IT0
Crossbar
GATE0
TH0
Reload
(8 bits)
IN0PL
XOR
/INT0
Figure 26.2. T0 Mode 2 Block Diagram
26.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The coun-
ter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0
and TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register
is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the
Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the
Timer 1 interrupt.
Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0,
1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However,
the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode set-
tings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1,
configure it for Mode 3.
Rev. 1.1
269
SILICON [ SILICON ]
