SIO1007 datasheet(29/108 Pages) MICROCHIP

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DS00002020A-page 29

SIO1007

The transmitter FIFO empty indications will be delayed 1 character time minus the last stop bit time whenever

the following occurs: THRE=1 and there have not been at least two bytes at the same time in the transmitter FIFO

since the last THRE=1. The transmitter interrupt after changing FCR0 will be immediate, if it is enabled.

Character timeout and RCVR FIFO trigger level interrupts have the same priority as the current received data available

interrupt; XMIT FIFO empty has the same priority as the current transmitter holding register empty interrupt.

9.5

FIFO Polled Mode Operation

With FCR bit 0 = "1" resetting IER bits 0, 1, 2 or 3 or all to zero puts the UART in the FIFO Polled Mode of operation.

Since the RCVR and XMITTER are controlled separately, either one or both can be in the polled mode of operation. In

this mode, the user's program will check RCVR and XMITTER status via the LSR. LSR definitions for the FIFO Polled

Mode are as follows:

Bit 0=1 as long as there is one byte in the RCVR FIFO.

Bits 1 to 4 specify which error(s) have occurred. Character error status is handled the same way as when in the interrupt

mode, the IIR is not affected since EIR bit 2=0.

Bit 5 indicates when the XMIT FIFO is empty.

Bit 6 indicates that both the XMIT FIFO and shift register are empty.

Bit 7 indicates whether there are any errors in the RCVR FIFO.

There is no trigger level reached or timeout condition indicated in the FIFO Polled Mode, however, the RCVR and XMIT

FIFOs are still fully capable of holding characters.

Note 9-2

The percentage error for all baud rates, except where indicated otherwise, is 0.2%.

Note 9-3

The High Speed bit is located in the Device Configuration Space.

TABLE 9-3:

BAUD RATES

Desired Baud

Rate

Divisor Used to Generate

16X Clock

Percent Error Difference Between Desired

and Actual (Note 9-2)

High Speed

Bit (Note 9-3)

2304

0.001

1536

110

1047

134.5

857

0.004

150

768

300

384

600

192

1200

1800

2000

0.005

2400

3600

4800

7200

9600

19200

38400

0.030

57600

0.16

115200

0.16

230400

32770

0.16

460800

32769

0.16

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