GC4114 Datasheet, PDF (22/45 Pages) Texas Instruments – QUAD TRANSMIT CHIP

GC4114 QUAD TRANSMIT CHIP
DATA SHEET REV 1.0
5.6 COUNTER MODE REGISTER
Registers 6, and 7 set the counter’s cycle period.
ADDRESS 6:
Counter Byte 0, suggested default = 0xff
BIT
TYPE
0-7
R/W
NAME
CNT[0:7]
DESCRIPTION
The LSBs of the counter cycle period
ADDRESS 7:
Counter Byte 1, suggested default = 0xff
BIT
TYPE
NAME
DESCRIPTION
0-7
R/W
CNT[8:15]
The 8 MSBs of the counter cycle period
The chip’s internal sync counter counts in cycles of 128(CNT+1) clocks. A terminal count signal (TC) is
output at the end of each cycle. The counter can be synchronized to an external sync as specified in the Sync mode
Register (See Section 5.1). If CNT is set so that 128(CNT+1) is a multiple of twice the interpolation ratio (i.e., a
multiple of 16N), then the terminal count of this counter can be output on the SO pin and used to periodically
synchronize multiple GC4114 chips.
5.7 CHANNEL SYNC REGISTERS
Registers 8,9,10 and 11 control the synchronization modes of the four channels. The sync modes described
here are unique to each of the channels. The modes use the same settings as shown in Table 1 (See Section 5.1).
ADDRESS 8:
ADDRESS 9:
ADDRESS 10:
ADDRESS 11:
Channel-A Sync Modes, suggested default = 0x5f
Channel-B Sync Modes
Channel-C Sync Modes
Channel-D Sync Modes
BIT
TYPE
NAME
DESCRIPTION
0,1 LSB
R/W
FREQ_SYNC
The new frequency setting takes affect on this sync
2,3
R/W
PHASE_SYNC
The new phase offset takes affect on this sync
4,5
R/W
NCO_SYNC
The NCO is initialized to the phase setting by this sync
6,7 MSB
R/W
DITHER_SYNC
The dither circuit is initialized by this sync to zero.
The NCO_SYNC is usually set to be always off, unless the user wants to coherently control the phases of
multiple channels. The FREQ_SYNC and PHASE_SYNC are typically set to be always on so that frequency and
phase settings will take effect immediately as they are written into their control registers (See Section 5.0 addresses
32 to 63). Alternately, the FREQ_SYNC and PHASE_SYNC controls may be set to the SI or one shot modes to
allow the frequency and phase to be changed smoothly, or coherently with another event. The DITHER_SYNC is
used to turn on or off the dithering of the NCO phase. To turn off dithering set the DITHER_SYNC to be always on
so that it remains initialized to zero. To turn dithering on set the sync to be always off. During diagnostics the
NCO_SYNC and DITHER_SYNC should be set to “TC”.
Texas Instruments Inc.
- 18 -
MAY 22, 2000
This document contains information which may be changed at any time without notice