GC4114 Datasheet, PDF (19/45 Pages) Texas Instruments – QUAD TRANSMIT CHIP

GC4114 QUAD TRANSMIT CHIP
DATA SHEET REV 1.0
5.1 SYNC MODE REGISTER
The Sync mode control register determines how the circuits within the chip are synchronized. Each circuit
which requires synchronization can be configured to be synchronized to the sync input (SI), or to the terminal count
of the sync counter (TC). The sync to each circuit can also be set to be always on or always off. Each circuit is given
a two bit sync mode control which is defined as:
Table 1: Sync Modes
MODE
0
1
2
3
SYNC DESCRIPTION
“0” (never asserted)
SI
TC (or OS, if USE_ONESHOT is set)
“1” (always)
NOTE: the internal syncs are active high. The SI input has been inverted to be the active high sync SI.
ADDRESS 0:
Sync Mode, suggested default = 0x65
BIT
TYPE
NAME
DESCRIPTION
0,1 (LSBs) R/W
INT_SYNC
Synchronizes the interpolation control counter. The interpolation
counter controls the filtering of each channel.
2,3
R/W
COUNTER_SYNC
Synchronizes the sync counter. This counter is used to generate the
periodic “TC” sync pulses. Mode 2 is OS, not TC, for the counter.
4,5
R/W
OUTPUT_SYNC
The selected sync is inverted and output on the SO pin.
6
R/W
USE_ONESHOT
The terminal count mode in Table 1 is replaced by the one shot pulse
(OS) when this bit is set.
7
R/W
ONE_SHOT
The one shot sync pulse (OS) is generated when this bit is set. This
bit must be cleared before another one shot pulse can be generated.
If the user wishes to allow the chip to free run, asynchronous to other chips, then the sync settings can be
set to zero. If one wishes to synchronize several chips to a single sync source, then the sync mode selections should
be set to one. The suggested default is to output the one-shot (USE_ONESHOT = 1, OUTPUT_SYNC=2) and all
other syncs to SI. The user should tie the SO output pin of one GC4114 chip to the SI input pin of all other GC4114
chips in a system in order to cleanly synchronize and initialize one or more GC4114 chips. If there is only a single
GC4114 chip, then all sync mode selections can be set to “2” to receive the one-shot directly. A one-shot should be
sent after initialization and each time the interpolation ratio is changed.
Texas Instruments Inc.
- 15 -
MAY 22, 2000
This document contains information which may be changed at any time without notice