UM10147_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 28 April 2008
49 of 134
NXP Semiconductors
UM10147
P89LPC952/954 User manual
8.1 Mode 0
Putting either Timer into Mode 0 makes it look like an 8048 Timer, which is an 8-bit
Counter with a divide-by-32 prescaler.
shows Mode 0 operation.
In this mode, the Timer register is configured as a 13-bit register. As the count rolls over
from all 1s to all 0s, it sets the Timer interrupt flag TFn. The count input is enabled to the
Timer when TRn = 1 and either TnGATE = 0 or INTn = 1. (Setting TnGATE = 1 allows the
Timer to be controlled by external input INTn, to facilitate pulse width measurements).
TRn is a control bit in the Special Function Register TCON (
). The TnGATE bit is
in the TMOD register.
4
T1M0
Mode Select for Timer 1. These bits are used with the T1M2 bit in the TAMOD register to determine the
Timer 1 mode (see
).
5
T1M1
6
T1C/T
Timer or Counter Selector for Timer 1. Cleared for Timer operation (input from CCLK). Set for Counter
operation (input from T1 input pin).
7
T1GATE Gating control for Timer 1. When set, Timer/Counter is enabled only while the INT1 pin is high and the TR1
control pin is set. When cleared, Timer 1 is enabled when the TR1 control bit is set.
Table 36.
Timer/Counter Mode register (TMOD - address 89h) bit description
…continued
Bit Symbol
Description
Table 37.
Timer/Counter Auxiliary Mode register (TAMOD - address 8Fh) bit allocation
Bit
7
6
5
4
3
2
1
0
Symbol
--
-
-
T1M2
-
-
-
T0M2
Reset
x
x
x
0
x
x
x
0
Table 38.
Timer/Counter Auxiliary Mode register (TAMOD - address 8Fh) bit description
Bit Symbol
Description
0
T0M2
Mode Select for Timer 0. These bits are used with the T0M2 bit in the TAMOD register to determine the
Timer 0 mode (see
1:3 - reserved
4
T1M2
Mode Select for Timer 1. These bits are used with the T1M2 bit in the TAMOD register to determine the
Timer 1 mode (see
The following timer modes are selected by timer mode bits TnM[2:0]:
000 —
8048 Timer ‘TLn’ serves as 5-bit prescaler. (Mode 0)
001 —
16-bit Timer/Counter ‘THn’ and ‘TLn’ are cascaded; there is no prescaler.(Mode 1)
010 —
8-bit auto-reload Timer/Counter. THn holds a value which is loaded into TLn when it overflows.
(Mode 2)
011 —
Timer 0 is a dual 8-bit Timer/Counter in this mode. TL0 is an 8-bit Timer/Counter controlled by the
standard Timer 0 control bits. TH0 is an 8-bit timer only, controlled by the Timer 1 control bits (see text).
Timer 1 in this mode is stopped. (Mode 3)
100 —
Reserved. User must not configure to this mode.
101 —
Reserved. User must not configure to this mode.
110 —
PWM mode (see
111 —
Reserved. User must not configure to this mode.
5:7 -
reserved