AC37 High-Speed Communication Adapter Card
REGISTER DEFINITION
MODEM STATUS REGISTER:
OFFSET 6 - READ ONLY
This register is associated with modems in name only. The AC37 does not support modem control, but this register
has been provided to allow the status of other features to be obtained. The bits are defined below:
Bit 0:
IRQ Line Status
This bit is set to a logic 1 whenever the Remote Bus IRQ line is being driven to the
active state by a device other than the AC37. Bit 0 functions identically to bit 4.
Bit 1:
Not Used
This bit is not used and will always read as a logic 0.
Bit 2:
CPU Interrupt Request
This bit is set to a logic 1 when the CPU of the AC37 is requesting to interrupt the host
CPU. This feature is for future product enhancements. Current operating modes of the
AC37 will not generate this interrupt and this bit will read as a logic 0. Bit 2 functions
identically to bit 6.
Bit 3:
Not Used
This bit is not used and will always read as a logic 0.
Bit 4:
IRQ Line Status
This bit is set to a logic 1 whenever the Remote Bus IRQ line is being driven to the
active state by a device other than the AC37. Bit 4 functions identically to bit 0. Bit 4 is
the CTS status bit in a 16,550 UART chip.
Bit 5:
Address/Data Receive Flag
When the AC37 is operating in 9 bit mode, this bit is used to indicate the status of the
9th bit of the last byte read from the receive FIFO. If the AC37 is being used to monitor
a Remote I/O link using binary protocol, this bit will indicate whether the received byte
was an address or data. If the last byte read was an address byte, bit 5 will be set to a
logic 1. Bit 5 will be set to a logic 0 if the last byte read from the receive FIFO was
designated as a data byte. The status of this bit is only affected by a read from the
receive FIFO.
Bit 6:
CPU Interrupt Request
This bit is set to a logic 1 when the CPU of the AC37 is requesting to interrupt the host
CPU. This feature is for future product enhancements. Current operating modes of the
AC37 will not generate this interrupt and this bit will read as a logic 0. Bit 6 functions
identically to bit 2.
Bit 7:
Not Used
This bit is not used and will always read as a logic 0.
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