MS51
Dec. 17, 2019
Page
208
of 316
Rev 1.01
M
S51
SE
RIES
TE
CHNICA
L REF
ERE
N
CE MA
NU
A
L
TCON
– Timer 0 and 1 Control
Regiser
Address
Reset Value
TCON
88H, all pages, Bit-addressable
0000_0000b
7
6
5
4
3
2
1
0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
R/W
R/W
R/W
R/W
R (level)
R/W (edge)
R/W
R (level)
R/W (edge)
R/W
Bit
Name
Description
7
TF1
Timer 1 overflow flag
This bit is set when Timer 1 overflows. It is automatically cleared by hardware when the program
executes the Timer 1 interrupt service routine. This bit can be set or cleared by software.
6
TR1
Timer 1 run control
0 = Timer 1 Disabled. Clearing this bit will halt Timer 1 and the current count will be preserved in
TH1 and TL1.
1 = Timer 1 Enabled.
5
TF0
Timer 0 overflow flag
This bit is set when Timer 0 overflows. It is automatically cleared via hardware when the program
executes the Timer 0 interrupt service routine. This bit can be set or cleared by software.
4
TR0
Timer 0 run control
0 = Timer 0 Disabled. Clearing this bit will halt Timer 0 and the current count will be preserved in
TH0 and TL0.
1 = Timer 0 Enabled.
3
IE1
External interrupt 1 edge flag
If IT1 = 1 (falling edge trigger), this flag will be set by hardware when a falling edge is detected. It
remain set until cleared via software or cleared by hardware in the beginning of its interrupt service
routine.
If IT1 = 0 (low level trigger), this flag follows the inverse of the
INT1
̅̅̅̅̅̅̅
input
signal’s logic level.
Software cannot control it.
2
IT1
External interrupt 1 type select
This bit selects by which type that
INT1
̅̅̅̅̅̅̅
is triggered.
0 =
INT1
̅̅̅̅̅̅̅
is low level triggered.
1 =
INT1
̅̅̅̅̅̅̅
is falling edge triggered.
1
IE0
External interrupt 0 edge flag
If IT0 = 1 (falling edge trigger), this flag will be set by hardware when a falling edge is detected. It
remain set until cleared via software or cleared by hardware in the beginning of its interrupt service
routine.
If IT0 = 0 (low level trigger), this flag follows the inverse of the
INT0
̅̅̅̅̅̅̅
input signal’s logic level.
Software cannot control it.
0
IT0
External interrupt 0 type select
This bit selects by which type that
INT0
̅̅̅̅̅̅̅
is triggered.
0 =
INT0
̅̅̅̅̅̅̅
is low level triggered.
1 =
INT0
̅̅̅̅̅̅̅
is falling edge triggered.
TL0
– Timer 0 Low Byte
Regiser
Address
Reset Value
TL0
8AH, all pages
0000_0000b
7
6
5
4
3
2
1
0
TL0[7:0]
