Watchdog Modes; Watchdog Pulse (Mode 9) - Motorola DSP56303 User Manual

Operating Modes
9.3.4

Watchdog Modes

The following watchdog timer modes are provided:
n
Watchdog Pulse
n
Watchdog Toggle

9.3.4.1 Watchdog Pulse (Mode 9)

Bit Settings
TC3 TC2 TC1
1 0 0
In Mode 9, the timer generates an external signal at a preset rate. The signal period is equal to
the period of one timer clock. After the counter reaches the value in the TCPR, if the
TCSR[TRM] bit is set, the counter is loaded with the TLR value on the next timer clock and
the count resumes. Therefore TRM = 1 is not useful for watchdog functions. If the
TCSR[TRM] bit is cleared, the counter continues to increment on each subsequent timer
clock. This process repeats until the timer is disabled (that is, TCSR[TE] is cleared). If the
counter overflows, a pulse is output on the
clock period. If the INV bit is set, the pulse polarity is high (logical 1). If INV is cleared, the
pulse polarity is low (logical 0). The counter reloads when the TLR is written with a new
value while the TCSR[TE] bit is set. In Mode 9, internal logic preserves the
direction for an additional 2.5 internal clock cycles after the hardware
asserted. This convention ensures that a valid
resets the DSP56303.
9-22
TC0 Mode Name
1 9
TIO
DSP56303 User's Manual
Mode Characteristics
Function
Pulse Watchdog
signal with a pulse width equal to the timer
signal is generated when the
RESET
TIO Clock
Output Internal
value and
TIO
signal is
RESET
signal
TIO