PMAC PCI-Lite Hardware Reference Manual
22
Software Setup
If the CPU’s operational frequency has been determined by (a non-zero setting of) I46, the serial
communications baud rate is determined at power-up/reset by variable I54 alone according to the
following table:
I54
Baud Rate
I54
Baud Rate
0 600 8
9600
1 900 9
14,400
2 1200 10
19,200
3 1800 11
28,800
4 2400 12
38,400
5 3600 13
57,600
6 4800 14
76,800
7 7200 15 115,200*
* The CPU must be run at an exact multiple of 30MHz in order to use 115,200
baud serial communications. Otherwise, the baud rate will not be exact enough to
ensure proper communications.
The card number (0 – 15) for serial addressing of multiple cards on a daisy chain serial cable is
determined by variable I0. Jumpers E40 – E43 determine the direction of the phase and servo clocks. All
of these jumpers must be ON for the card to use its internally generated clock signals and to output these
on the serial port connector. If any of these jumpers is OFF, the card will expect to input these clock
signals from the serial port connector, and its watchdog timer will trip immediately if it does not receive
these signals.
Serial Addressing Card Number
I0 controls the card number for software addressing purposes on a multi-drop serial communications
cable. If I2 is set to 2, the PMAC must be addressed with the @n command where
n
matches the value of
I0 on the board, before it will respond. If the PMAC receives the @n command where
n
does not match
I0 on the board, it will stop responding to commands on the serial port. No two boards on the same serial
cable may have the same value of I0.
If the @@ command is sent over the serial port, all boards on the cable will respond to action commands.
However, only the board with I0 set to 0 will respond to the host with handshake characters and/or data
responses. All boards on the cable will respond to control-character action commands such as <CTRL-
R>, regardless of the current addressing.
Note:
RS422 serial interfaces must be used on all PMAC boards for multi-drop serial
communications. This will not work with RS232 interfaces. Typically, multiple
PMAC boards on the same serial cable will share servo and phase clock signals
over the serial port cable for tight synchronization. If the servo and phase clock
lines are connected between multiple PMACs, only one of the PMAC boards can
be set up to output these clocks (E40 – E43 all ON for a PMAC PCI Lite). All of
the other boards in the chain must be set up to input these clocks (one or more of
the jumpers E40 – E43 OFF for a PMAC PCI Lite).
Any PMAC PCI Lite board with one or more of E40 – E43 OFF is expecting its Servo and Phase clock
signals externally from a Card 0. If it does not receive these clock signals, the watchdog timer will
immediately shut down the board and the red LED will light.
If the PMAC PCI Lite is set to receive external Servo and Phase clock signals for synchronization
purposes, but is not using multi-drop serial communications, I0 does not need to be changed from 0.
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