CD2231 Intel Corporation, CD2231 Datasheet - Page 38
Manufacturer Part Number
CD2231 Intelligent Two-channel Lan And Wan Communications Controller
CD2231 — Intelligent Two-Channel LAN and WAN Communications Controller
Figure 4. Interrupt Acknowledge Cycle
Interrupt vector is always on A/D[0–7].
Groups and Types
There are two general reasons for the CD2231 to request service from the host processor — data
transfer and exceptional conditions. Furthermore, interrupts are grouped into three categories, each
with an associated Interrupt Request signal — IREQ1*, IREQ2*, and IREQ3*.
Group 1 — Modem signal change/timer events
Group 2 — Transmit interrupts
Group 3 — Receive interrupts
Group 1 is only used for exceptions. Groups 2 and 3 include both data transfer and exceptions.
shows the possible causes of transmit and receive interrupt service requests. The cause of
an interrupt request is encoded into the two least-significant bits of the vector presented on the data
bus during the interrupt acknowledge cycle. The most-significant six bits of the vector come from
Interrupt Vector LSBs
Modem signal change or timer event
Transmit data or exception
Receive Good Data
SAMPLES ADDRESS BUS