
Chapter 14. Timers/Counters and Serial Interface Page 14-1
Chapter 14 Timers/Counters and Serial Interface
14.1 Introduction
The FX2’s timer/counters and serial interface are very similar to the standard 8051’s, with some dif-
ferences and enhancements. This chapter provides technical information on configuring and using
the timer/counters and serial interface.
14.2 Timers/Counters
The FX2 includes three timer/counters (Timer 0, Timer 1, and Timer 2). Each timer/counter can
operate either as a timer with a clock rate based on the FX2’s internal clock (CLKOUT) or as an
event counter clocked by the T0 pin (Timer 0), T1 pin (Timer 1), or the T2 pin (Timer 2). Timers 1
and 2 may be used for baud clock generation for the serial interface (see Section 14.3 for details of
the serial interface).
The FX2 can be configured to operate at 12, 24, or 48 MHz. In “timer” mode, the timer/counters run
at the same speed as the FX2, and they are not affected by the CLKOE and CLKINV configuration
bits (CPUCS.1 and CPUCS.2).
Each timer/counter consists of a 16-bit register that is accessible to software as two SFRs:
• Timer 0 — TH0 and TL0
• Timer 1 — TH1 and TL1
• Timer 2 — TH2 and TL2
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