DS89C420 Datasheet, PDF (35/59 Pages) Dallas Semiconductor – Ultra-High-Speed Microcontroller

DS89C420
on the corresponding T0/T1 pin for 1-to-0 transitions. The mode of operation is controlled by the timer
mode (TMOD) register. Each timer consists of a 16-bit register in 2 bytes, which can be found in the SFR
map as TL0, TH0, TL1, and TH1. Timers 0 and 1 are enabled by the timer control (TCON) register.
Table 13. Timer Functions
FUNCTIONS
TIMER 0
Timer/Counter
13/16/8^*/2 x 8 bit
Timer with Capture
No
External Control-Pulse Counter
Yes
Up/Down Auto-Reload Timer/Counter
No
Baud Rate Generator
No
Timer-Output Clock Generator
No
* 8-bit timer/counter includes auto-reload feature; 2 x 8-bit mode does not.
TIMER 1
13/16/8^* bit
No
Yes
No
Yes
No
TIMER 2
16 bit
Yes
No
Yes
Yes
Yes
Timer 2 is a true 16-bit timer/counter that, with a 16-bit capture (RCAP2L and RCAP2H) register, is able
to provide some unique functions like up/down auto-reload timer/counter and timer-output clock
generation. Timer 2 (registers TL2 and TH2) is enabled by the T2CON register, and its mode of operation
is selected by the T2MOD register.
Each timer has a selectable time base (Table 15). Following a reset, the timers default to divide by 12 to
maintain drop-in compatible with the 8051. If Timer 2 is used as a baud rate generator or clock output, its
time base is fixed at divide by 2, regardless of the setting of its timer mode bits.
For details of operation, refer to “Programmable Timers” in the Ultra-High-Speed Flash Microcontroller
User’s Guide.
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