| ALTERA_JTAG_UART(4) | Device Drivers Manual | ALTERA_JTAG_UART(4) |
altera_jtag_uart —
driver for the Altera JTAG UART Core
device altera_jtag_uart
In /boot/device.hints:
hint.altera_jtag_uart.0.at="nexus0"
hint.altera_jtag_uart.0.maddr=0x7f000000
hint.altera_jtag_uart.0.msize=0x40
hint.altera_jtag_uart.0.irq=0
hint.altera_jtag_uart.1.at="nexus0"
hint.altera_jtag_uart.1.maddr=0x7f001000
hint.altera_jtag_uart.1.msize=0x40
The altera_jtag_uart device driver
provides support for the Altera JTAG UART core, which allows multiple
UART-like streams to be carried over JTAG.
altera_jtag_uart allows JTAG UART streams to be
attached to both the low-level console interface, used for direct kernel
input and output, and the tty(4) layer, to be used with
ttys(5) and login(1). Sequential Altera
JTAG UART devices will appear as ttyu0,
ttyu1, etc.
Altera JTAG UART devices can be connected to using Altera's
nios2-terminal program, with the instance selected
using the --instance argument on the management
host. altera_jtag_uart supports JTAG UART cores with
or without interrupt lines connected; if the irq
portion of the device.hints entry is omitted, the
driver will poll rather than configure interrupts.
Altera Embedded Peripherals IP User Guide, Altera Corporation, http://www.altera.com/literature/ug/ug_embedded_ip.pdf, June 2011.
The altera_jtag_uart device driver first
appeared in FreeBSD 10.0.
The altera_jtag_uart device driver and
this manual page were developed by SRI International and the University of
Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
(“CTSRD”), as part of the DARPA CRASH research programme. This
device driver was written by Robert N. M.
Watson.
altera_jtag_uart must dynamically poll to
detect when JTAG is present, in order to disable flow control in the event
that there is no receiving endpoint. Otherwise, the boot may hang waiting
for the JTAG client to be attached, and user processes attached to JTAG UART
devices might block indefinitely. However, there is no way to flush the
output buffer once JTAG is detected to have disappeared; this means that a
small amount of stale output data will remain in the output buffer, being
displayed by nios2-terminal when it is connected.
Loss of JTAG will not generate a hang-up event, as that is rarely the
desired behaviour.
nios2-terminal does not place the
client-side TTY in raw mode, and so by default will not pass all control
characters through to the UART.
| August 18, 2012 | Debian |