STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
Register 044H: BTIF Bit Offset
Bit
Type
Function
Default
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Unused
Unused
Unused
Unused
BOFF_EN
BOFF[2]
BOFF[1]
BOFF[0]
X
X
X
X
0
0
0
0
R/W
R/W
R/W
R/W
BOFF_EN:
The bit offset enable (BOFF_EN) bit is used to enable the bit offset bits. If
BOFF_EN is a logic 0, the bit offset is disabled and there is no bit offset
between the frame pulse and the first bit of the first time slot. In this case, the
BOFF[2:0] bits are ignored. If BOFF_EN is a logic 1, the bit offset is enabled
and the BOFF[2:0] bits operate as described below.
BOFF[2:0]:
The bit offset (BOFF[2:0]) bits gives a binary representation of the fixed offset
between the backplane transmit frame pulse (BTFP) and the start of the first
bit of the first time slot. This binary representation is then used to determine
the BTCLK edge, defined as CER (clock edge receive) on which the first bit
of the first time slot is sampled. For example, if CER is 4, the data on
BTPCM and BTSIG is sampled on the fourth clock edge after BTFP is
sampled (see Figure 11). The following tables show the relationship between
BOFF[2:0], FE, DE and CER.
PROPRIETARY AND CONFIDENTIAL
164
PMC [ PMC-SIERRA, INC ]
