Table 8. Serial Mode Register Functions
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
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
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.
June 14, 2000
Proprietary Information and Specifications are Subject to Change