CD2481 Datasheet, PDF (41/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

Programmable Four-Channel Communications Controller — CD2481
Figure 4. Interrupt Acknowledge Cycle
IREQn*
IACKIN*
DS*
R/W*, CS*
A/D[0–15]
CD2481
SAMPLES ADR BUS
VECTOR*
A[0–7]
DTACK*
1 CLOCK
DELAY
DEN*
DATDIR*
* INTERRUPT VECTOR IS ALWAYS ON A/D[0–7]
5.2.3
Groups and Types
There are two general reasons for the CD2481 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.
Table 2 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
the LIVR and are user defined:
Interrupt Vector LSBs
00
Receive exception
01
Modem signal change or timer event
10
Transmit data or exception
11
Receive Good Data
Datasheet
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