MC68336/376
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
8-32
the same way, each time the result is written for a CCW with the pause bit set, the
queue pause flag is set, and when enabled, an interrupt request is generated.
Table 8-5 displays the status flag and interrupt enable bits which correspond to queue
1 and queue 2 activity.
Both polled and interrupt-driven QADC operations require that status flags must be
cleared after an event occurs. Flags are cleared by first reading QASR with the appro-
priate flag bits set to one, then writing zeros to the flags that are to be cleared. A flag
can be cleared only if the flag was a logic one at the time the register was read by the
CPU. If a new event occurs between the time that the register is read and the time that
it is written, the associated flag is not cleared.
8.13.2 Interrupt Register
The QADC interrupt register QADCINT specifies the priority level of QADC interrupt
requests and the upper six bits of the vector number provided during an interrupt
acknowledge cycle.
The values contained in the IRLQ1 and IRLQ2 fields in QADCINT determine the prior-
ity of QADC interrupt service requests. A value of %000 in either field disables the
interrupts associated with that field. The interrupt levels for queue 1 and queue 2 may
be different.
The IVB[7:2] bits specify the upper six bits of each QADC interrupt vector number.
IVB[1:0] have fixed assignments for each of the four QADC interrupt sources. Refer to
8.13.3 Interrupt Vectors
When the QADC is the only module with an interrupt request pending at the level being
acknowledged, or when the QADC IARB value is higher than that of other modules
with requests pending at the acknowledged IRQ level, the QADC responds to the inter-
rupt acknowledge cycle with an 8-bit interrupt vector number. The CPU32 uses the
vector number to calculate a displacement into the exception vector table, then uses
the vector at that location to jump to an interrupt service routine.
The interrupt vector base field IVB[7:2] specifies the six high-order bits of the 8-bit
interrupt vector number, and the QADC provides two low-order bits which correspond
to one of the four QADC interrupt sources.
Table 8-5 QADC Status Flags and Interrupt Sources
Queue
Queue Activity
Status Flag
Interrupt Enable Bit
Queue 1
Result written for the last CCW in queue 1
CF1
CIE1
Result written for a CCW with pause bit set in
queue 1
PF1
PIE1
Queue 2
Result written for the last CCW in queue 2
CF2
CIE2
Result written for a CCW with pause bit set in
queue 2
PF2
PIE2