CD1865 Datasheet, PDF (38/150 Pages) Intel Corporation – Intelligent Eight-Channel Communications Controller

CD1865 — Intelligent Eight-Channel Communications Controller
Figure 8. Three-Level Interrupt with Three-Level Acknowledge Example
IPL1
IPL2
IPL3
M68000
MICROPROCESSOR
EIGHT-LEVEL
PRIORITY
ENCODER
AS*
A8–A23
A4–A7
A1–A3
D0–D7
ADDRESS
DECODE
LOGIC
RREQ*
TREQ*
MREQ*
ACKOUT*
ACKIN*
CD1865 # 2
D0–D7
CS*
A3–A6
A0–A2
RREQ*
TREQ*
MREQ*
ACKIN*
ACKOUT*
CD1865 # 1
D0–D7
CS*
A3–A6
A0–A2
5.5.2
Method 1b — Full Interrupt – Type B, Three-Level
Interrupt with Single-Level Acknowledge
This method is illustrated in Figure 9. It is useful with 80X86 systems that use the 8259A Interrupt
Controller. Since the 8259A supplies its own vector to the host when an INTA cycle occurs, the
host can simply read the CD1865’s vector by the method described in the polled interface example
or a separate device select decode can be provided to drive the ACKIN* input.
After the 8259A supplies a vector to the 80X86 host CPU, the host performs a software
acknowledgment to the CD1865, and transfers the CD1865 vector to the host. This allows the
service request to be processed.
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Datasheet