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NTWOC(4) NetBSD Kernel Interfaces Manual NTWOC(4)
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ntwoc -- Riscom/N2, N2pci, WANic 400 synchronous serial interfaces
ntwoc* at pci? dev ? function ? flags 0
ntwoc0 at isa? port 0x300 irq 5 iomem 0xc8000 flags 1
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 asynchro-
nous/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
Currently clock source and speed information is specified with the flags
locator in the kernel configuration file. The flags field has the fol-
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 trans-
mit 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 fre-
quency 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:
Line clock with noise suppression.
txs0 txs1 Specifies which clock source to use for transmitting data on
port 0 and port 1 respectively. The following values are
np (For the ISA card only) A value of 1 indicates there is a sec-
ond serial port present on the card. This is auto-detected on
the PCI card and need not be specified.
Cards supported by the ntwoc driver include:
SDL Communications Riscom/N2
SDL Communications N2pci
SDL Communications WANic 400 (untested)
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 trans-
fers 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.
intro(4), isa(4), pci(4), ifconfig(8)
The PCI driver first appeared in NetBSD 1.4. Much of the ISA driver was
adapted from the FreeBSD sr driver and first appeared in NetBSD 1.5.
Use of the flags locator for setting the clock sources and speeds should
be replaced with ioctl's and a control program.
NetBSD 9.99 October 2, 1998 NetBSD 9.99