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
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.
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 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.
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.