NAME
ntwoc
- Riscom/N2, N2pci, WANic 400 synchronous serial interfaces
SYNOPSIS
ntwoc* at pci? dev ? function ? flags 0
ntwoc0 at isa? port 0x300 irq 5 iomem 0xc8000 flags 1
DESCRIPTION
The
ntwoc
device driver supports bit-synchronous serial communication using
Cisco HDLC framing.
The cards are capable of being driven by
the line clock or from an internal baud rate generator.
The devices all use the Hitachi hd64570 serial chip.
The hd64570 supports 2 asynchronous/byte-synchronous/bit-synchronous
serial ports, and has a 4-channel DMA controller for loading
the serial port FIFOs.
The ISA Riscom/N2 card has a jumper block to set the IRQ and a DIP switch
to set the port address the card will use.
The values programmed into the card must be specified with the
port
and
irq
locators in the kernel configuration line.
The
iomem
locator must be specified and must occur on a 16k boundary.
The driver uses a 16k region of io memory.
Bit 0 of the
flags
locator indicates if there is a second serial port available on the
card.
Currently
clock source and speed information is specified with the
flags
locator in the kernel configuration file.
The flags field has the following format.
3 2 1
1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+-------------+ +-----+ +-----+ + +---+ +-+ + +---+ +-+ +
tmc tdiv rdiv e1 rxs1 ts1 e0 rxs0 txs0 np(*)
- tmc
-
Defines the timer constant.
The base clock frequency is divided by
tmc
to generate the main clock for receiving and sending.
Further division is possible with the
tdiv
and
rdiv
divisor options.
A value of 0 is treated as 256.
- tdiv
-
Defines the transmit divisor as
2^(tdiv).
The internal transmit clock
frequency is determined by dividing the base clock frequency by
tmc
and then dividing by
2^(tdiv).
- rdiv
-
Defines the receive divisor as
2^(rdiv).
The internal receive clock
frequency is determined by dividing the base clock frequency by
tmc
and then dividing by
2^(rdiv).
- e0 e1
-
If true the internal clock source is used to drive the line clock for port 0
or port 1 respectively.
- rxs0 rxs1
-
Specifies which clock source to use for receiving data on port 0 and
port 1 respectively.
The following values are accepted:
- 0
-
Line clock.
- 1
-
Line clock with noise suppression.
- 2
-
Internal clock.
- txs0 txs1
-
Specifies which clock source to use for transmitting data on port 0
and port 1 respectively.
The following values are accepted:
- 0
-
Line clock.
- 1
-
Internal clock.
- 2
-
Receive clock.
- np
-
(For the ISA card only)
A value of 1 indicates there is a second serial
port present on the card.
This is auto-detected on the PCI card and need not be specified.
HARDWARE
Cards supported by the
ntwoc
driver include:
-
SDL Communications Riscom/N2
-
SDL Communications N2pci
-
SDL Communications WANic 400 (untested)
DIAGNOSTICS
- ntwoc0: TXDMA underrun - fifo depth maxed
-
Indicates that the serial port's FIFO is being drained faster
than DMA can fill it.
The driver automatically increases the low-water mark at which to
begin DMA transfers when underruns occur.
This diagnostic is issued when the low-water mark is
maximized (i.e., 1 less than the depth of the FIFO).
- ntwoc0: RXDMA buffer overflow
-
Indicates that a frame is being received by the card, but
there are no free receive buffers.
SEE ALSO
intro(4),
isa(4),
pci(4),
ifconfig(8)
HISTORY
The PCI driver first appeared in
NetBSD1.4.
Much of the ISA driver was adapted from the
FreeBSD
sr
driver and first appeared in
NetBSD1.5.
BUGS
Use of the
flags
locator for setting the clock sources and speeds should be replaced with
ioctl's and a control program.