CD2481 Datasheet, PDF (96/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

CD2481 — Programmable Four-Channel Communications Controller
Table 15. Bisync Receive State Transition (Sheet 2 of 2) (see “Key” on page 96)
Character
Received
BGETHDR
0
BESCF
1
BESCL
2
BGETxT
3
BBCC
4
BBCC2
5
BWEOT BXP BDIS
6
7
8¹
ETB
RxITB = 0
PAD
none of above
RxITB = 0
none of above
RxITB = 1
6
6
6
3 i CRC
hunt
hunt
hunt
hunt
4 CRC
0-RxITB
7 CRC
4 CRC
0-RxITB
3 CRC
5 CRC
5 CRC
CRC ^b
CRC ^b
7 CRC
3 CRC 5 CRC CRC ^b
7 CRC
3 CRC 5 CRC CRC ^b
6
7
CRC
8
hunt
0-RxITB
7
CRC
hunt
6
7
CRC
8
6
7
CRC
8
1.The BDIS’ state is entered on receipt of error.
2.In the BBCC2 state, if RxITB = 1, go to state BGETHDR, else go to syn hunt.
3.If RxITB = 1, then calculate BCC, else do not calculate BCC.
4.IF SOHf-1 and EBCDIC, then calculate BCC, else do not calculate BCC. If in ASCII/LRC mode, initialize BCC. Else do not
calculate nor initialize BCC.
5.If in ASCII/LRC mode, but overridden by the DLE-STX, then initialize BCC, else calculate BCC.
Key
hunt
i
CRC
0
1
STXf
SOHf
= Go to syn hunt state
= initialize BCC
= calculate CRC
= clear state flag for example, 0-RxITB clears the RxITB flag
= set state flag
= STX first flag
= SOH first flag
Note: When returning to the syn-hunt state, RxITB is cleared.
Equation 1. State Descriptions
Number
Name
Description
0
BGETHDR SYN-SYN received, and looking for next non-SYN character.
1
BESCF The first DLE after opening SYNs has been received.
2
BESCL A DLE has been received, but not the first for this frame.
3
BGETXT
The first non-SYN character after opening SYNs has been received, and that first
character is either: STX, SOH, or a non-organized character if RxITB=1.
A proper end of text has been received, and the channel is ready for the first BCC
4
BBCC character. The things considered proper are: ETX, ETB, or ITB in non-transparent.
Or, DLE-ETX, DLE-ETB, or DLE-ITB in transparent.
5
BBCC2
The first BCC character has been received, and the chip is ready for the second
BCC character.
6
BWEOT Continue receiving in this state until a PAD is detected.
7
BXP
Transparent receive. Look for escape DLE. Else, keep receiving.
8
BDIS
Disconnect state. Nothing being received. Remains in this state until a PAD is
received.
96
Datasheet