Microcontroller User's Manual

MOTOROLA Chapter 23. UART Modules 23-5
Register Descriptions
Table 23-2 describes UMR1n fields.
Table 23-2. UMR1n Field Descriptions
Bits Name Description
7 RxRTS Receiver request-to-send. Allows the RTS output to control the CTS input of the transmitting device to prevent
receiver overrun. If both the receiver and transmitter are incorrectly programmed for RTS
control, RTS control
is disabled for both. Transmitter RTS control is configured in UMR2n[TxRTS].
0 The receiver has no effect on RTS
.
1 When a valid start bit is received, RTS is negated if the UART's FIFO is full. RTS is reasserted when the FIFO
has an empty position available.
6 RxIRQ/
FFULL
Receiver interrupt select.
0 RxRDY is the source that generates IRQ or DMA request.
1 FFULL is the source that generates IRQ or DMA request.
5 ERR Error mode. Configures the FIFO status bits, USRn[RB,FE,PE].
0 Character mode. The USRn values reflect the status of the character at the top of the FIFO. ERR must be 0 for
correct A/D flag information when in multidrop mode.
1 Block mode. The USRn values are the logical OR of the status for all characters reaching the top of the FIFO
since the last
RESET ERROR STATUS command for the channel was issued. See Section 23.3.5, “UART
Command Registers (UCRn).”
4–3 PM Parity mode. Selects the parity or multidrop mode for the channel. The parity bit is added to the transmitted
character, and the receiver performs a parity check on incoming data. The value of PM affects PT, as shown
below.
2 PT Parity type. PM and PT together select parity type (PM = 0x) or determine whether a data or address character is
transmitted (PM = 11).
PM Parity Mode Parity Type (PT= 0) Parity Type (PT= 1)
00 With parity Even parity Odd parity
01 Force parity Low parity High parity
10 No parity n/a
11 Multidrop mode Data character Address character
1–0 B/C Bits per character. Select the number of data bits per character to be sent. The values shown do not include start,
parity, or stop bits.
00 5 bits
01 6 bits
10 7 bits
11 8 bits