Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 8- 23
Disabled—TOUTx is disabled and three-stated.
Toggle Mode—If the timer is disabled (SWR = 0) when this encoding is programmed,
TOUTx is immediately set to zero. If the timer is enabled (SWR = 1), timeout events
(counter reaches $0000) toggle TOUTx. In the input capture/output compare mode,
TOUTx is immediately set to zero if the timer is disabled (SWR = 0). If the timer is
enabled (SWR = 1), timer compare events toggle TOUTx. (Timer compare events occur
when the counter reaches the value stored in the COM.)
Zero Mode—If the timer is disabled (SWR = 0) when this encoding is programmed,
TOUTx is immediately set to zero. If the timer is enabled (SWR = 1), TOUTx will be set
to zero at the next timeout. In the input capture/output compare mode, TOUTx is
immediately set to zero if the timer is disabled (SWR = 0). If the timer is enabled (SWR
= 1), TOUTx will be set to zero at timeouts and set to one at timer compare events. If
the COM is $0000, TOUTx will be set to zero at the timeout/timer compare event.
One Mode—If the timer is disabled (SWR = 0) when this encoding is programmed,
TOUTx is immediately set to one. If the timer is enabled (SWR = 1), TOUTx will be set
to one at the next timeout. In the input capture/output compare mode, TOUTx is
immediately set to one if the timer is disabled (SWR = 0). If the timer is enabled (SWR =
1), TOUTx will be set to one at timeouts and set to zero at timer compare events. If the
COM is $0000, TOUTx will be set to one at the timeout/timer compare event.
8.4.4 Status Register (SR)
The SR contains timer status information as well as the state of the prescaler. This
register is updated on the rising edge of the system clock when a read of its location is not
in progress, allowing the most current information to be contained in this register. The
register can be read, and the TO, TG, and TC bits can be written when the timer module is
enabled (i.e., the STP bit in the MCR is cleared).
SR $608, $648
1514131211109876543210
IRQ TO TG TC TGL ON OUT COM PO7 PO6 PO5 PO4 PO3 PO2 PO1 PO0
RESET (TGATE≈ NEGATED):
0000100011111111
RESET (TGATE≈ ASSERTED):
0000000011111111
Supervisor/User
IRQ—Interrupt Request bit
The positioning of this bit in the most significant location in this register allows it it be
conditionally tested as if it were a signed binary integer.
1 = An interrupt condition has occurred. This bit is the logical OR of the enabled TO,
TG, and TC interrupt bits.
0 = The bit(s) that caused the interrupt condition has been cleared. If an
IRQ≈ signal
has been asserted, it is negated when this bit is cleared.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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