4-10
Serial Interface
Baud Rate Clocks
4.3
Baud Rate Clocks
A 19.66 MHz clock signal generated by the MACIO is used to derive a
baud rate clock for all of the SCCs. This is divided by four before being fed
to the SCCs at 4.915 MHz. The baud rate can be changed by loading
different time constants (which can be different for each channel) into the
time constant register. The clocking modes 1, 2, 16, 32 and 64 are
supported.
The SCCs can be operated at baud rates of between 75 and 19200. This is
controlled by the clocking mode and the contents of the time constant
register. The value of the time constant can be determined using the
following equation:
For example, to set a baud rate of 9600 using the x16 clocking mode on the
SPARCbook, the following would be used:
This gives a time constant of approximately 14 (0xD).
4.4
Handshakes
With the exception of the mouse and keyboard port, the serial channels all
support handshaking. The handshake signals are controlled or monitored
via the write registers and read registers of the associated SCC channel.
Tc
Clock
2
Mode
(
)
×
Buadrate
(
)
×
--------------------------------------------------------------------
2
–
=
Tc
4.915
6
10
×
2
16
×
9600
×
------------------------------
2
–
=
S3GX_TRMBook Page 10 Friday, September 19, 1997 11:39 am
Содержание SPARCbook 3 series
Страница 1: ...Series Technical Reference Manual 980327 02 3 S3GX_TRMBook Page i Friday September 19 1997 11 39 am...
Страница 8: ...viii S3GX_TRMBook Page viii Friday September 19 1997 11 39 am...
Страница 28: ...1 16 Architecture Overview Microcontroller Subsystem S3GX_TRMBook Page 16 Friday September 19 1997 11 39 am...
Страница 44: ...2 16 The SPARC CPU SBus Controller S3GX_TRMBook Page 16 Friday September 19 1997 11 39 am...
Страница 76: ...5 8 SCSI Controller DMA Support S3GX_TRMBook Page 8 Friday September 19 1997 11 39 am...
Страница 82: ...6 6 Ethernet Interface DMA Support for Network Operations S3GX_TRMBook Page 6 Friday September 19 1997 11 39 am...
Страница 96: ...7 14 PCMCIA Interface Microcontroller Registers S3GX_TRMBook Page 14 Friday September 19 1997 11 39 am...
Страница 146: ...9 28 MODEM Class 2 Fax Command Set S3GX_TRMBook Page 28 Friday September 19 1997 11 39 am...
Страница 180: ...11 30 Display Interface RAMDAC S3GX_TRMBook Page 30 Friday September 19 1997 11 39 am...
Страница 210: ...B 10 Connector Information Removable Hard Drive SCSI Connector S3GX_TRMBook Page 10 Friday September 19 1997 11 39 am...
Страница 216: ...Index vi S3GX_TRMBook Page vi Friday September 19 1997 11 39 am...