CD2231

Manufacturer Part NumberCD2231
DescriptionCD2231 Intelligent Two-channel Lan And Wan Communications Controller
ManufacturerIntel Corporation
CD2231 datasheet
 
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CD2231 — Intelligent Two-Channel LAN and WAN Communications Controller
the assertion of a modem interrupt request. It is cleared when the host CPU writes to
the Modem End of Interrupt register.
Bit 5
Meo
Modem end of interrupt is set automatically when the host CPU writes to the Modem
End of Interrupt register while in a modem interrupt routine.
Bit 4
Reserved – always returns ‘0’ when read.
Bits 3:2
Mvct [1:0]
Modem Vector bits are set by the CD2231 to provide the lower two bits of the vector
supplied to the host CPU during an interrupt acknowledge cycle. Modem vector is
decoded as follows: Mvct [1] = 0, and Mvct [0] = 1.
Bit 1
Reserved – always returns ‘0’ when read.
Bit 0
Mcn [0]
Modem channel number is set by the CD2231 to indicate the channel requiring
modem interrupt service.
8.5.4.3
Modem (/Timer) Interrupt Status Register (MISR)
Register Name: MISR
Register Description: Modem Interrupt Status
Default Value: x’00
Access: Byte Read/Write
Bit 7
Bit 6
Bit 5
DSRChg
CDChg
CTSChg
When the host receives a modem interrupt, the following status is provided in this register:
Bit 7
DSR changed
A logic ‘1’ indicates that a change has been detected on the DSR* input. The change
detect is programmed in COR4 and COR5.
Bit 6
CD changed
A logic ‘1’ indicates that a change has been detected on the CD* input. The change
detect is programmed in COR4 and COR5.
Bit 5
CTS changed
A logic ‘1’ indicates that a change has been detected on the CTS* input. The change
detect is programmed in COR4 and COR5.
Bits 4:2
Unused; returns ‘0’ when read
Bit 1
General Timer 2 timed-out (count reaches zero before being reset or disabled).
Bit 0
General Timer 1 timed-out (count reaches zero before being reset or disabled).
138
Men
Mact
Meo
Sequence of Events
0
0
0
Idle
1
0
0
Modem interrupt requested, but not asserted
1
1
0
Modem interrupt asserted
0
1
0
Modem interrupt acknowledged
0
0
1
Modem interrupt service routine completed
Bit 4
Bit 3
0
0
Intel Hex Address: x’88
Motorola Hex Address: x’8B
Bit 2
Bit 1
Bit 0
0
Timer2
Timer1
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