Interrupt Register (Ir); Control Register (Cr) - Motorola MC68340 User Manual

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
15 14 13 12
0 0 0 0
RESET:
0 0 0 0
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
15 14 13 12
SWR IE2 IE1 IE0
RESET:
0 0 0 0
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.
8-20
Freescale Semiconductor, Inc.
11 10 9 8
0 IL2 IL1 IL0
0 0 0 0
11 10 9 8
TGE PCLK CPE CLK
0 0 0 0
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7 6 5 4
IVR7 IVR6 IVR5 IVR4
0 0 0 0
7 6 5 4
POT2 POT1 POT0 MODE2 MODE1 MODE0
0 0 0 0
$604, $644
3 2 1 0
IVR3 IVR2 IVR1 IVR0
1 1 1 1
Supervisor Only
$606, $646
3 2 1 0
OC1 OC0
0 0 0 0
Supervisor/User
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