Typewriter User Manual

8- 20 MC68340 USER’S MANUAL MOTOROLA
8.4.2 Interrupt Register (IR)
The IR contains the priority level for the timer interrupt request and the 8-bit vector number
of the interrupt. The register can be read or written to at any time while in supervisor mode
and while the timer module is enabled (i.e., the STP bit in the MCR is cleared).
IR $604, $644
1514131211109876543210
00000IL2IL1IL0IVR7 IVR6 IVR5 IVR4 IVR3 IVR2 IVR1 IVR0
RESET:
0000000000001111
Supervisor Only
Bits 15–11—Reserved
IL2–IL0—Interrupt Level Bits
Each module that can generate interrupts has an interrupt level field. The priority level
encoded in these bits is sent to the CPU32 on the appropriate
IRQ≈ signal. The CPU32
uses this value to determine servicing priority. See Section 5 CPU32 for more
information.
IV7–IV0—Interrupt Vector Bits
Each module that can generate interrupts has an interrupt vector (IV) field. This 8-bit
number indicates the offset from the base of the vector table where the address of the
exception handler for the specified interrupt is located. The IV field is reset to $0F,
which indicates an uninitialized interrupt condition. See Section 5 CPU32 for more
information.
8.4.3 Control Register (CR)
The CR controls the operation of the timer. The register can always be read or written
when the timer module is enabled (i.e., the STP bit in the MCR is cleared). Changing the
contents of the CR should only be attempted when the timer is disabled (the SWR bit in
the CR is cleared). Changing the CR while the timer is running may produce unpredictable
results.
CR $606, $646
1514131211109876543210
SWR IE2 IE1 IE0 TGE PCLK CPE CLK POT2 POT1 POT0 MODE2 MODE1 MODE0 OC1 OC0
RESET:
0000000000000000
Supervisor/User
SWR—Software Reset
1 = Removes the software reset.
0 = A software reset is performed by first clearing this bit and then clearing the TO,
TG, and TC bits in the SR. The prescaler is loaded with $FF, the counter is set to
$0000, and the SR COM bit is cleared. When this bit is zero, the timer is
disabled.
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cale Semiconductor,
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