AM8530H AMD [Advanced Micro Devices], AM8530H Datasheet - Page 93

• Manufacturer Part Number: AM8530H
• Description: Serial Communications Controller
• Manufacturer: AMD [Advanced Micro Devices]

Data Communication Modes Functional Description
The SYNC input falling edge (synchronized through some internal circuitry) essentially
removes the Receiver from “Hunt Mode” in which it is waiting for synchronization before
accepting Receive Data. Upon exiting “Hunt Mode”, the Receiver will begin accepting all
incoming Receive Data. To cause the Am85C30 to discontinue accepting data (i.e. notify
the Am85C30 that there is an end of frame), the “Enter Hunt Mode” command must be
issued. The SYNC line should remain low for at least the TwSY (SYNC* Pulse Width)
specification value, and may be kept low for a longer duration of time if desired.
4.10.2.5.1 SDLC External SYNC Mode
By programming WR4 as shown below both the receiver and transmitter will be placed in
SDLC mode. The only variation from normal SDLC operation will be that the SYNC pin
will be used to start or stop the reception of a frame by forcing the receiver to act as
though a flag had been received.
4.10.2.5.2 Synchronous External SYNC Mode
By programming WR4 as shown below the transmitter will be configured for MONOSYNC
operation and the SYNC pin will be used to start the reception of a message.
SIGNAL
DATA
0
1
0
D7
Figure 4–26. External SYNC Message Format
?
D6
0
1
0
?
EXTERNAL SYNC
D7 D6 D5 D4 D3 D2 D1 D0
1
D5
1
WR4—Register Layout
WR4—Register Layout
1
programming either of these bit
patterns specifies that only the SYNC
pin can be used for character sync
either the SYNC pin or a match with
the character stored in WR7 will signal
character sync
D4
1
1
1
D3
0
0
DATA
D2
0
0
D1
?
?
CRC
D0
?
?
1
CRC
2
AMD
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