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M4641-20

Baseband Processor for GSM Applications

Conexant Systems 

M46

Baseband Processor

Table 8. Serial Mode Register Functions

Bit

Signal

15:4 N/A

3

Counting Disable

2

Clock Select

1:0 N/A

Function

Reserved

Enable/disable timer counting

Select the timer counting clock:

Timer A (SIM interface):

0 = SIM clock selected as the counting clock.

1 = SIM ETU clock selected as the counting clock.

Timer B (general purpose timing):

0 = ARM clock (19.5 MHz) selected as the counting clock.

1 = system clock (3.9 MHz) selected as the counting clock.

Reserved. “00” must be written to these bits.

Serial Port Registers _________________________________

There are eight serial port registers:

• Serial Buffer Registers (In and Out)

• Serial Mode Register

• Serial Port Interrupt Register

• Serial Port Line Register

• Serial Port Status Register

• Serial Port Form Register

• Serial Out Divider Register

• Serial In Divider Register

All of the Serial Port Registers are eight bits wide. The address

and default values for the serial port registers are specified in

Table 2.

Serial Buffer Registers. The Serial In and Serial Out Buffer

Registers are located at the same address. The Serial In Buffer

Register is read only and contains data that is received at the

input to the port. The Serial Out Buffer Register is write only and

contains data that is transmitted at the output of the port.

Serial Mode Register. The contents of the Serial Mode

Register determine the operating mode of the serial port. The

function of each bit in this register is described in Table 8.

Serial Port Interrupt Register. The Serial Port Interrupt

Register contains the flags for all of the serial port interrupts and

the enables for each of these interrupts. The function of each bit

in this register is described in Table 9. Bits [4:0] are read/write.

Bits [7:5] are read only.

Serial Port Line Register. The contents of the Serial Port Line

Register specify the data formatting of input and output serial

data. Parity, word length, and start/stop bits are all configured by

this register. All bits in the register are read/write. The function

of each bit in this register is described in Table 10.

Serial Port Status Register. The Serial Port Status Register

provides information on the status of the port. All bits are read

only and may be read by the ARM processor or the DMA

Controller. The function of each bit in this register is described in

Table 11.

Serial Port Form Register. The Serial Port Form Register is

used to specify the duration of the last stop bit in the serial

transmit data stream and to control the IrDA pulse shaper

circuit. Bits [1:0] specify the duration of the last stop bit.

Normally, the last stop bit is one bit in length. If it is necessary to

use shorter stop bits, the Serial Out Divider Register must be

loaded with 0x0F. The stop bit length for each of the possible

values of bits [1:0] is specified in Table 12. All bits in the Serial

Port Form Register are read/write.

18

June 14, 2000

Conexant

Proprietary Information and Specifications are Subject to Change

100779C

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