CD1865 datasheet(78/150 Pages) INTEL

78 / 150 page

CD1865 — Intelligent Eight-Channel Communications Controller

Datasheet

The remote device can signal the CD1865 to resume transmission in one of two ways depending on

the setting of the Implied Xon mode (IXM) option bit COR2. When the IXM bit is set, the CD1865

resumes transmission upon receipt of any character, for example, each character is an implied Xon.

In Implied Xon mode it is assumed that if the remote is capable of transmitting data, it is able to

receive as well. If a character is treated as an implied Xon, no special status is recorded in the

RCSR, and the TxFlon bit is not set in the CCSR. An implied Xon character is not stripped if flow-

control transparency is enabled.

When the IXM bit is not set, the CD1865 only resumes transmission upon receipt of an Xon

character. In addition, the host may force a resumption of transmission by issuing a Transmit

Enable Command, which clears the TxFloff bit. The Xon and Xoff characters or character

sequences are equal in a Toggle mode. There is no special bit to enable this mode. The CD1865

detects this mode whenever the Xon character equals the Xoff character, and it implements Toggle

mode automatically.

In Toggle mode, whenever the special character is received, the current state of flow control is

toggled. If flow control transparency is set, the character is dropped. If not in flow-control

transparency, the character is passed to the host. If it is a single character, the special character

status is ‘1’ and the character is put in the Receive Data FIFO. In two-character sequence, the

second character is placed in the Receive Data FIFO along with special character ‘1’ in the Status

FIFO.

The TxFloff and TxFlon bits indicate channel status when the remote device is flow-controlling the

CD1865 transmitter. When the remote requests the CD1865 to stop transmission, the CD1865 sets

the TxFloff Status bit in the CCSR. If TxFloff is set, the last flow-control character received was a

flow-off. When the remote sends an explicit flow-on character, the CD1865 clears the TxFloff bit,

and set the TxFlon bit. (If flow is resumed because of implied Xon, TxFloff is cleared, but TxFlon

is not set). When the CD1865 resumes transmission, the TxFlon bit is cleared. Transmit Flow

Status bits is also cleared by enabling or disabling the transmitter or resetting the channel.

This is summarized in the table below:

7.4

Modem Signals and General-Purpose I/O

Each channel of the CD1865 has four pins that can be used either as modem-control or general-

purpose input/output pins. The modem signal names assigned to these four pins have been chosen

to provide an easy reference for systems designers. In fact, they are all simply general purpose

inputs and outputs (if automatic Out-of-Band Flow Control is not used) that can be individually

controlled by the modem signal value register(s). Since they are general purpose, system designers

may choose to connect the pins in any way that suits the application.

TxFloff

TxFlon

Meaning

Illegal

Transmitter is flow-controlled off

Transmitter on, no data sent yet

Transmitter on, CD1865 has sent data, or implied Xon has

occurred. This is also the ‘normal’ state of these bits when flow

control is not being used

CD1865 Datasheet(PDF) 78 Page - Intel Corporation

CD1865 Datasheet(HTML) 78 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