AC37 High-Speed Communication Adapter Card
MODEM CONTROL REGISTER:
OFFSET 4 – READ/WRITE
This register is associated with modems in name only. The AC37 does not support modem control. This register has
been provided to support other features, in this case the secondary interrupt. The secondary interrupt feature on
AC37 is used by the Remote Bus IRQ line. Only one bit in the register is used for this purpose; other bits are not used.
There are two basic versions of the AC37 in the field: an older full-length card and a newer half-size card. The newer
card supports the use of this bit to enable interrupts. The older AC37 does not support the use of this bit; however,
we recommend that the bit still be set to ensure compatibility with all versions.
NOTE: If you are using Windows NT, you must use the newer AC37, and its U5 must be labeled 9087. Earlier
versions will not work with NT.
Bits 0–2:
Not Used
Bit 3:
Secondary Interrupt Enable
This bit is cleared upon power-up reset and must be set for the secondary interrupt to
be enabled.
Bits 4–7:
Not Used
2-7
REGISTER DEFINITION
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