CD1865 datasheet(73/150 Pages) INTEL

73 / 150 page

Intelligent Eight-Channel Communications Controller — CD1865

Datasheet

When the CD1865 receiver is too busy, the transmitter can be used to send Xoff/Xon to the remote

device. This Receiver Software (In-Band) Flow Control is covered in Section 7.3.3 on page 74.

The CD1865 transmitter can be controlled by the remote device. This Transmitter Software (In-

Band) Flow Control is covered in Section 7.3.6 on page 76.

The current flow-control status is always available to the host. It is stored in the Channel Control

Status register (CCSR). Two bits, Receive Flow-on and Receive Flow-off, show whether the last

flow-control command sent by the CD1865 was on or off. As long as the receiver is enabled, the

CD1865 continues to receive any data sent regardless of whether it has requested the remote to shut

off.

7.3.2

Receiver Hardware (Out-of-Band) Flow Control

Out-of-Band Flow Control uses the Modem Handshake signal (DTR*) to control the flow of data.

Whenever the Receive FIFO reaches a user-defined threshold, DTR* is negated. This event can be

used to signal the remote to stop sending characters. The threshold is set by four bits in the Modem

Control Option register 1, and can be any level from one to eight, or disabled. The DTR* pin is also

negated whenever DTR* mode is set and the channel is disabled or reset. If DTR* mode is not set,

the DTR* pin is not changed by the CD1865, and remains at whatever value the host sets it to.

While it is possible to set the DTR* threshold lower than the service request threshold, the part

operates as though the DTR* threshold was the same as the service request threshold. If the DTR*

threshold is set lower, it is ignored, and DTR* negates when the service request threshold is

reached. If required, set the DTR* threshold to a ‘1’, and then it ‘tracks’ the other threshold

automatically.

Figure 25. Receiver Flow-Control Logic

RECEIVER SHIFT REGISTER

RECEIVER HOLDING REGISTER

FULL/

EMPTY

BIT

RECEIVER FIFO, STATUS FIFO

BACKGROUND CODE:

H.R.-TO-FIFO TRANSFER, OTHER

FEATURES. FLOW CONTROL:

FOREGROUND CODE:

BIT ASSEMBLY,

S.R.-TO-H.R. TRANSFER

(INTERRUPT-DRIVEN)

(POLLING LOOP)

DTR

OUT

DSR

MATCH SPECIAL CHARACTER?

DSR* ASSERTED?

DTR* THRESHOLD REACHED?

CD1865 Datasheet(PDF) 73 Page - Intel Corporation

CD1865 Datasheet(HTML) 73 Page - Intel Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL