SAB 82525
SAB 82526
SAF 82525
SAF 82526
Transmit Address Byte 1 (WRITE)
7
0
XAD1 2-byte address
XAD1 (high byte)
XAD1 (COMMAND)
0
(0)
(24/64)
1-byte address
XAD1 (and XAD2) can be programmed with one individual address byte which is appended
automatically to the frame by HSCX in auto-mode. The function depends on the selected
address mode (bit ADM in MODE).
– 2-byte address field (MODE.ADM = 1)
XAD1 forms the high byte of the 2-byte address field. Bit 1 must be set to 0! According to the
ISDN LAPD protocol, bit 1 is interpreted as the C/R (COMMAND/RESPONSE) bit. This is
manipulated automatically by the HSCX dependent on the setting of the CRI bit in RAH1:
Bit 1 (C/R)
Commands transmit
Responses transmit
1
0
0
1
CRI = 1
CRI = 0
(In the ISDN, the high address byte is known as SAPI).
In accordance with the HDLC protocol, bit 0 should be set to 0, indicating the extension of the
address field to two bytes.
– 1-byte address field (MODE.ADM = 0)
According with the X.25 LAPB protocol, XAD1 indicates a COMMAND.
Semiconductor Group
92
SIEMENS [ Siemens Semiconductor Group ]
