Delta Tau Geo Brick, User Manual

Page: 102 / 294

Geo Brick Drive User Manual
Pinouts and Software Setup 102
Global Control Registers
X:$78BnF (default value: $18000B) where n=2 for axes 1-4
n=3 for axes 5-8
Global Control Register
Axes 1-4 X:$78B2F
Axes 5-8 X:$78B3F
The Global Control
register is used to program the serial encoder interface clock frequency SER_Clock
and configure the serial encoder interface trigger clock. SER_Clock is generated from a two-stage divider
clocked at 100 MHz as follows:
M N Clock Frequency
49 0 2.0 MHz
99 0 1.0 MHz
99 1 500.0 KHz
99 2 250.0 KHz
… …
Default Settings: M=24, N=0 => 4 MHz transfer rates
There are two external trigger sources; phase and servo. Bits [9:8] in the Global Control
register are used
to select the source and active edge to use as the internal serial encoder trigger. The internal trigger is
used by all four channels to initiate communication with the encoder. To compensate for external system
delays, this trigger has a programmable 4-bit delay setting in 20 μsec increments.
23--16 15--12 11 10 9 8 7 6 5 4 3 2 1 0
M_Divisor N_Divisor Trigger Clock Trigger Edge Trigger Delay Protocol Code
Bit Type Default Name Description
[23:16] R/W 0x18 M_Divisor
Intermediate clock frequency for SER_Clock . The
intermediate clock is generated from a (M+1) divider clocked
at 100 MHz.
[15:12] R/W 0x0 N_Divisor
Final clock frequency for SER_Clock . The final clock is
generated from a
N
2
divider clocked by the intermediate
clock.
[11:10] R 00 Reserved Reserved and always reads zero.
[09] R/W 0 TriggerClock
Trigger clock select: 0= PhaseClock
1= ServoClock
[08] R/W 0 TriggerEdge
Active clock edge select: 0= rising edge
1= falling edge
[07:04] R/W 0x0 TriggerDelay
Trigger delay program relative to the active edge of the
trigger clock. Units are in increments of 20 usec.
[03:00] R 0xB ProtocolCode
This read-only bit field is used to read the serial encoder interface
protocol supported by the FPGA. A value of
$B defines this
protocol as BiSS .