CD1284 Datasheet, PDF (118/176 Pages) Intel Corporation – IEEE 1284-Compatible Parallel Interface Controller with Two High-Speed Asynchronous Serial Ports

CD1284 — IEEE 1284-Compatible Parallel Interface Controller
7.2.8
Virtual Registers — All
End of Service Request Register
Register Name: EOSRR
Register Description: End of Service Request
Access: Write only
Bit 7
Bit 6
Bit 5
X
X
X
Bit 4
X
Bit 3
X
Bit 2
X
8-Bit Hex Address: 60
Default Value: XX
Bit 1
X
Bit 0
X
The EOSRR is a dummy location used to signal the end of a hardware service-acknowledge
procedure invoked by the activation of SVCACK*. The data pattern written is a ‘don’t care’ value.
A write to this location causes the CD1284 to perform its internal switch out of the service-
acknowledge context. This register is only used during a hardware-activated service acknowledge
and must not be written during Poll-mode operation.
7.3
7.3.1
Channel Registers
Each of the four channels has a set of registers that control aspects of its operation. In the following
register descriptions the register contents and offsets apply to any of the channels; the channel
being accessed at any given time is controlled by the CAR. This is true even during a service-
acknowledge context; the CAR points to the channel to be serviced, whether it was loaded by the
host (during Poll-mode operation) or by the CD1284 itself (during a hardware-activated service
acknowledge).
Channel Command Register
Register Name: CCR
Register Description: Channel Command
Access: Read/Write
Bit 7
Bit 6
Bit 5
Res Chan
COR Chg
Send SC
Bit 4
Chan Ctl
Bit 3
D3
Bit 2
D2
8-Bit Hex Address: 05
Default Value: 00
Bit 1
D1
Bit 0
D0
The CCR issues commands directly to the on-chip processor to control or change some channel
and, in one case, global functions of the channel selected by the CAR. The upper four bits indicate
which of four command types is being issued and the lower four bits are parameters to those
commands. No more than one bit is ever set in the command type field. When the command is
executed by the CD1284, it zeros out the CCR. Therefore, two consecutive commands must wait
for the CCR to clear after the first is issued, before the second command is issued.
Note:
The CCR is valid only for serial channels 2 and 3. Commands issued to the CCR location of the
parallel channel (channel 0) or channel 1 are ignored by the MPU and have no effect on device
operation. If the host needs to issue a full device reset, it must select either channel 2 or channel 3
before issuing the command.
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Datasheet