參數(shù)資料
型號: CD1865
廠商: Intel Corp.
英文描述: Intelligent Eight-Channel Communications Controller
中文描述: 智能八通道通信控制器
文件頁數(shù): 40/150頁
文件大?。?/td> 871K
代理商: CD1865
CD1865
Intelligent Eight-Channel Communications Controller
40
Datasheet
5.5.4
Method 3b
Polled Interface
This method is illustrated in
Figure 11
. Polled operation can be used with any type of host CPU, or
it can be used in combination with interrupts to provide a mixed-mode system optimized for a
particular application. In a polled system, the host reads the Service Request Status register (SRSR)
within the CD1865 to determine whether there are any channels that need service. (Note that unlike
traditional UARTs, only one register needs to be read to determine if there are any channels in any
device that need attention, and this saves time).
If the host finds channels needing service, it acknowledges the required type by reading one of the
three Request Acknowledge registers. These provide a vector that can be used to jump directly to
the correct service routine. Processing from this point proceeds as in the case of interrupt-driven
operation. Note that the difference between this method and Method 2b lies in how the host system
becomes aware of the need to service the CD1865. In Method 2b a single interrupt starts the
process. In Method 3b the host polls periodically. The two methods can be combined
an
interrupt triggers the first service, but the host continues to poll until any other pending requests are
serviced.
Figure 10. Single-Level Interrupt with Single-Level Acknowledge Example
CD1865 # 1
CD1865 # 2
MICROPROCESSOR
ADDRESS
DECODE
LOGIC
A1
A3
A8
A23
A4
A7
D0
D7
ALE
INT
A0
A2
A3
A6
CS*
D0-D7
RREQ*
TREQ*
MREQ*
A0
A2
A3
A6
CS*
D0
D7
RREQ*
TREQ*
MREQ*
ACKIN* ACKOUT*
ACKOUT* ACKIN*
OR
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