SERIAL I/O (SIO) PORT

SPx_CON (Continued)

Address:

1F83H, 1F8BH

x = 0–1 (8XC196MH)

Reset State:

00H

The serial port control (SPx_CON) register selects the communications mode and enables or disables the receiver, parity checking, and nine-bit data transmission.

8XC196MH

7

M2

DIR

PAR

TB8

 

 

 

 

0

REN

PEN

M1

M0

 

 

 

 

Bit

Bit

 

 

 

Function

Number

Mnemonic

 

 

 

 

 

 

 

 

 

 

 

3

REN

Receive Enable

 

 

 

Setting this bit enables receptions. When this bit is set, a falling edge on

 

 

the RXDx pin starts a reception in mode 1, 2, or 3. In mode 0, this bit must

 

 

be clear for transmission to begin and must be set for reception to begin.

 

 

Clearing this bit stops a reception in progress and inhibits further

 

 

receptions. To avoid a partial or undesired reception, clear this bit before

 

 

clearing the RI flag in SPx_STATUS. This can be handled in an interrupt

 

 

environment by using software flags or in straight-line code by using the

 

 

interrupt pending register to signal the completion of a reception.

 

 

 

 

 

2

PEN

Parity Enable

 

 

 

 

In modes 1 and 3, setting this bit enables the parity function. This bit must

 

 

be cleared if mode 2 is used. When this bit is set, TB8 takes the parity

 

 

value on transmissions and SPx_STATUS.7 becomes the receive parity

 

 

error bit.

 

 

 

 

 

 

1:0

M1:0

Mode Selection

 

 

 

These bits along with bit 7 select the communications mode.

 

 

M2

M1

M0

 

 

 

0

0

0

synchronous mode 0

 

 

X

0

1

mode 1

 

 

X

1

0

mode 2

 

 

X

1

1

mode 3

 

 

1

0

0

synchronous mode 4

 

 

 

 

 

 

Figure 7-6. Serial Port Control (SPx_CON) Register (Continued)

7-11

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Intel 8XC196MD, 8XC196MH, 8XC196MC manual Bit Function