Sun Microsystems Ultra 5, Руководство по обслуживанию

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Appendix C Functional Description C-23
C.1.6.2 Serial Communications Controller
The Siemens serial communications controller enables a two-channel increased
throughput because of 32-byte first-in-first-out (FIFO) architecture. Serial port A
(DB25 connector) is fully synchronous/asynchronous, while serial port B
(DB9 connector) is asynchronous only. The serial communications controller has
64-byte buffering on both input and output. Therefore, the serial ports take less CPU
bandwidth. Interrupts are driven when the buffer is half full. The controller has a
dedicated crystal that enables using integer dividers to achieve exact baud rates in
most cases. The serial communications controller supports rates up to 921.6 Kbaud.
The limitation is the line drivers, which support up to 460.8 Kbaud.
The serial communications controller operates up to 430 Kbaud in asynchronous
mode. Synchronous mode operation is up to 460 Kbaud with external clocks.
The line drivers used are compatible with RS232 and RS423 protocols and are set
with a jumper on the motherboard. The slew rate of the line drivers is
programmable. The system slew rates are set at 10 VDC per microsecond for baud
rates greater than 100 Kbaud, and at 5 VDC per microsecond for baud rates less than
100 Kbaud. The following figure is a functional block diagram of the
communications controller serial ports.
FIGURE C-12
Communications Controller Serial Ports Functional Block Diagram
C.1.6.3 Flash PROM
The flash PROM is an 8-Mbit, 5.0 VDC, 1-Mbyte by 8-bit flash memory. The 1 Mbyte
of data is divided into 16 sectors of 64 Kbytes of flexible erase capability. This device
is designed to be programmed in-system with the standard system 5.0 VDC VCC
supply. 12.0 VDC Vpp is not required for program or erase operations. The flash
PROM is also programmed in a standard EPROM programmer. The flash PROM has
an access time of approximately 120 nanoseconds.
EBus2
XT
AL
UC5170
RC
Netw
or
k
DB25
DB9
UC5180
A
B
A
B
Serial
communications
controller