CD1865 Datasheet, PDF (106/150 Pages) Intel Corporation – Intelligent Eight-Channel Communications Controller

CD1865 — Intelligent Eight-Channel Communications Controller
9.2.3.5
Global Channel Registers 1
Register Name:
Register Description: Global Service Channel Register 1
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
Bit 5
Bit 4
Binary Value
C2
Bit 3
C1
Bit 2
C0
8-Bit Hex Address: $41
Intel Hex Address: $82
Motorola Hex Address: $83
Bit 1
Bit 0
Binary Value
9.2.3.6
Global Channel Registers 2
Register Name:
Register Description: Global Service Channel Register 2
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
Bit 5
Bit 4
Binary Value
C2
Bit 3
C1
Bit 2
C0
8-Bit Hex Address: $42
Intel Hex Address: $84
Motorola Hex Address: $85
Bit 1
Bit 0
Binary Value
9.2.3.7
Global Channel Registers 3
Register Name:
Register Description: Global Service Channel Register 3
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
Bit 5
Bit 4
Binary Value
C2
Bit 3
C1
Bit 2
C0
8-Bit Hex Address: $43
Intel Hex Address: $86
Motorola Hex Address: $87
Bit 1
Bit 0
Binary Value
There are three registers used to provide the channel number of the channel requesting service.
Reading any of these registers causes the CD1865 to ‘mask-in’ three bits, specifying the channel
number of the currently active channel. Normally these registers are read by the host when it is
handling a service request. In this case, the three bits are the number of the channel requesting
service. If any of the three registers are read when the CD1865 is not in a service request context,
the three bits are the current value in the CAR. Bits 4:2 are masked into the contents of this register
by the CD1865 when it is read by the host. The actual contents of the register are not modified.
These three registers are provided as a convenience to the user. In most applications, the user uses
one of these locations, and sets the register to an arbitrary value. All types of service routines
would use this register. However, in some cases it may be useful to be able to record information
about the state of the CD1865 (or the software driving it) that is associated with each of the three
service request types. In this case, the user may associate an individual register with each level of
service request, and store whatever information is required in the unused bits. When entering a
service routine, the software can check these bits (a sub-vector) to read recorded states.
106
Datasheet