Table 10-1 Timer Modes Andc; F Eatures - Toshiba TX79 Series User Manual

10.1 Features
The TX7901 Programmable Timer/Counters consist of three timer "channels", Timer 0,
Timer 1, and Timer 2. Timer 0 operates only in the Interval Timer Mode. Timer 1 is capable
of operating only in the Interval Timer and Pulse Generation Modes. Timer 2 is capable of
operating in the Interval Timer, Pulse Generator, and Watchdog Timer Modes. All three
modes of operation utilize a 24-bit up counter. There is one counter per timer channel. The
three counter modes operate as described below.
10.1.1 Interval Timer Mode
In this mode, the timer generates periodic interrupts and can be configured to use internal or
external clock inputs to trigger the counter. The external clock input can be configured to
trigger the counter on its rising or falling edge.
10.1.2 Pulse Generator Mode
In this mode, the Timer output can be configured to provide waveforms of specific frequency
and duty ratio.
10.1.3 Watchdog Timer Mode
In this mode, the timer monitors and times out system runaway conditions.
10.1.4 Internal or External Clock Division
The internal or external clock source selected for a particular counter may be individually
scaled down to 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, or 1/256 of its input frequency.
Note: When using an external clock, its frequency should be less than or equal to one half that of the internal G-
Bus clock (i.e. less than or equal to 33/25 MHz).
Mode
Interval Timer
Pulse Generator
Watchdog Timer
TX7901 User's Manual (Rev. 6.30T – Nov, 2001)
Chapter 10: Programmable Timer/Contents
10. Programmable Timer/Counters
Table 10-1 Timer Modes and Channels
Description
Periodic interrupt
Provides waveform of specified frequency and
duty rate.
Detects runaway condition. Causes NMI or
sysReset.
10-1
Channel
0 1 2