Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 954

CPM Interrupt Controller
0
Field VN
Reset
R/w
Addr
Table 35-4 describes CIVR fields.
Source," and Section 35.7, "Interrupt Handler Example—Multiple-Event Interrupt Source,"
CIVR fields are used.
Bits Name
0–4 VN Vector number. Identifies the interrupt source. These values are listed in
5–14 — Reserved. Writing to bits 5-15 has no effect because they are always read as zeros.
15 IACK Interrupt acknowledge. When the core sets IACK, CIVR[VN] is updated with a 5-bit vector corresponding
to the sub-block with the highest current priority. IACK is cleared after one clock cycle.
35.6 Interrupt Handler Example—Single-Event Interrupt Source
In this example, the CPIC hardware clears CIPR[PC6] during the interrupt acknowledge cycle. The
following steps show how to handle an interrupt source without multiple events.
1. Set CIVR[IACK].
2. Read CIVR[VN] to determine the vector number for the interrupt handler.
3. Handle the interrupt event indicated through the port C6 signal.
4. Clear CISR[PC6].
5. Execute the rfi instruction.
35.7 Interrupt Handler Example—Multiple-Event Interrupt Source
In this example, CIPR[SCC2] remains set as long as one or more event bits remain unmasked in SCCE2.
This is an example of a handler for an interrupt source with multiple events. Notice that the handler must
clear the CISR bit but not the CIPR bit.
1. Set the CIVR[IACK].
2. Read CIVR[VN] to determine the vector number for the interrupt handler.
3. Immediately read the SCC2 event register into a temporary location.
4. Decide which events in the SCCE2 must be handled and clear those bits as soon as possible. SCCE
bits are cleared by writing ones.
5. Handle the events in the SCC2 Rx BD or Tx BD tables.
6. Clear CISR[SCC2].
35-10
4 5
0000_00000_0000_0000
Figure 35-5. CPM Interrupt Vector Register (CIVR)
Section 35.6, "Interrupt Handler Example—Single-Event Interrupt
Table 35-4. CIVR Field Descriptions
MPC885 PowerQUICC Family Reference Manual, Rev. 2
0
R/W
0x930
Description
Table
14 15
IACK
show how
35-2.
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