Quatech QSC(LP)-100 user manual Clock Rate Multiplier, RR1 RR0

Page 13

4.4.2 Clock Rate Multiplier

A standard RS-232 serial port operates at a clock speed of 1.8432 MHz. In order to achieve higher data rates, Quatech Enhanced Serial Adapters can operate at two times, four times or even eight times this standard clock speed. This is controlled by the clock rate multiplier bits in the Options Register.

Software can determine the UART clock frequency by reading the clock rate multiplier bits RR1 and RR0 in the Options Register as shown in Figure 11. RR1 and RR0 can be set by writing to the Options Register if the X2, X4, and X8 jumpers (J3-J5) are all removed. If one of these jumpers is applied, the RR1 and RR0 bits are forced to the appropriate value. Reading the Options Register will always return the clock rate multiplier at which the board is operating.

RR1

RR0

Clock Rate

UART Clock

Maximum Data

Multiplier

Frequency

Rate

 

 

0

0

X1

1.8432 MHz

115.2 kbaud

(default)

 

 

 

 

0

1

X2

3.6864 MHz

230.4 kbaud

1

0

X4

7.3728 MHz

460.8 kbaud

1

1

X8

14.7456 MHz

921.6 kbaud

Figure 11 --- Rate Register bit definition

At powerup and reset, the Options Register is initialized to 0. The QSC(LP)-100 will thus powerup in the x1 mode with software control of the clock rate multiplier enabled as long as the X2, X4, and X8 jumpers are not installed.

Software can control high baud rates through a combination of changing the clock rate multiplier and the UART baud rate divisor. For example, a baud rate of 230.4 kbps could be achieved by setting the clock rate multiplier to X2 mode (or by applying the X2 jumper) and setting a software application for 115.2 kbps.

QSC(LP)-100 User's Manual

13

Image 13
Contents QSCLP-100 Warranty Information Iii Declaration of Conformity Address Map and Special Registers Enable Scratchpad Register SPAD, J2Base Address and Interrupt Level IRQ Enhanced Serial Adapter IdentificationGeneral Information Factory Default Configuration Hardware ConfigurationClock multiplier jumper options Force High-Speed Uart Clock X2, X4, or X8, J3-J5Jumper/connector locations Hardware InstallationPort Address Range Interrupt Status Register Enabling the Special RegistersBit Name Description Options RegisterRR1 RR0 Clock Rate MultiplierWindows Millennium Windows ConfigurationsWindows Windows Using the New Hardware Found Wizard Viewing Resources with Device Manager Page Page Page Four-Port RS-232 Serial Adapter Page Page For legacy applicattions which cannot Page Page Windows NT Other Operating SystemsOS/2 DOS and other operating systemsQTPCI.EXE QTPCI.EXE Expert Mode display External Connections RS-232 Port Signal INTA# PCI Resource MapICL3245CA SpecificationsPage Computer will not boot up TroubleshootingQSCLP-100 Revision November