
Intelligent Eight-Channel Communications Controller
—
CD1865
Datasheet
101
In designs using register-based service acknowledgments (RRAR, TRAR, and MRAR), the
addresses of these registers must be placed in the equivalent Match register so that contains $75.
9.2.2.4
Transmit Service Match Register
This register must contain the value for Transmit Data Service Requests that are presented on the
Address Bus A0-A6 by the host to indicate the type of service request being acknowledged when
ACKIN* is asserted. This register, along with the other two Match registers, is compared to the
value on the Address Bus during acknowledgment cycles so that the CD1865 can determine the
service request being acknowledged by the host.
Bit 7 must be programmed to a
‘
1
’
. The CD1865 compares all eight bits internally, but there are
only seven address lines. Bits 6:0 of the register are compared to A6:A0 of the Address Bus. Bit 7
of the register is compared with a logic
‘
1
’
.
Within any one CD1865, the three Match registers must have unique values. In multiple-CD1865
designs where service acknowledgments are cascaded, all Match registers of the same type (for
example, Transmit) must have the same value.
In designs using register-based service acknowledgments (RRAR, TRAR, and MRAR), the
addresses of these registers must be placed in the equivalent Match register so that contains $76.
9.2.2.5
Receive Service Match Register
This register must contain the value for Receive Data Service Requests that are presented on the
Address Bus A0-A6 by the host to indicate the type of service request being acknowledged when
ACKIN* is asserted. This register, along with the other two Match registers, is compared to the
value on the Address Bus during acknowledgment cycles so that the CD1865 can determine the
service request being acknowledged by the host.
Bit 7 must be programmed to a
‘
1
’
. The CD1865 compares all eight bits internally, but there are
only seven address lines. Bits 6:0 of the register are compared to A6:A0 of the Address Bus. Bit 7
of the register is compared with a logic
‘
1
’
.
Register Name:
Register Description: Transmit Service Match Register
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
8-Bit Hex Address: $62
Intel Hex Address: $C4
Motorola Hex Address: $C5
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
Binary Value
Register Name:
Register Description: Receive Service Match Register
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
8-Bit Hex Address: $63
Intel Hex Address: $C6
Motorola Hex Address: $C7
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
Binary Value