GC4114 Datasheet, PDF (23/45 Pages) Texas Instruments – QUAD TRANSMIT CHIP

GC4114 QUAD TRANSMIT CHIP
DATA SHEET REV 1.0
5.8 CHANNEL FLUSH CONTROL REGISTER
This register controls flushing the four channels. Each channel is flushed when the selected sync occurs
The sync is selected according to Table 1 in Section 5.1.
ADDRESS 12: Channel Flush Register, suggested default = 0x55
BIT
TYPE
NAME
DESCRIPTION
0,1 LSB
R/W
2,3
R/W
4,5
R/W
6,7 MSB
R/W
FLUSH_A[0:1]
FLUSH_B[0:1]
FLUSH_C[0:1]
FLUSH_D[0:1]
The flush sync for channel A.
The flush sync for channel B.
The flush sync for channel C.
The flush sync for channel D.
Each channel needs to be flushed when the chip is being initialized or when the interpolation control is
changed. The flush lasts for 8N clocks after the sync occurs. The channel flush syncs will normally be left in a “never”
mode. If a channel is unused, then the user should leave the channel in the “always” flush mode which will clear the
datapath, clear the channel’s output, and lower its power consumption. During diagnostics the channels will need
to be flushed at the beginning of each sync cycle.
5.9 SUMMER MODE REGISTER
This register controls the output summer and round circuit.
ADDRESS 13: Summer Mode Register, suggested default = 0x09
BIT
0,1 LSB
2
TYPE
R/W
R/W
3
R/W
4
R/W
5
R/W
6
R/W
7 MSB
R/W
NAME
SUM_SCALE
SUM_DELAY
SUM_CLR
RND8
RND10
RND12
RND14
DESCRIPTION
The sum of the four channels is shifted down by SUM_SCALE
bits before being added to the sum-in signal.
The sum of the four channels is delayed by seven clock cycles
when this bit is high. This allows the outputs of two chips to be
coherently summed.
Clears the IN[0:15] inputs to the summer.
Round the output to 8 bits.
Round the output to 10 bits.
Round the output to 12 bits.
Round the output to 14 bits.
Only one of the round control bits should be set. If none are set, then the output is rounded to 16 bits. The
lower bits are rounded into the upper bits. Bits below the rounding point are cleared.
Texas Instruments Inc.
- 19 -
MAY 22, 2000
This document contains information which may be changed at any time without notice