Specifications

Serial Communications (V40)
Serial Data Format
The SCU supports asynchronous communication. The asynchronous
data format is shown in Figure 10-6 to include start, stop, and optional
parity bits, as well as seven or eight data bits.
The state of the TxD line, when data is not being transmitted, is the
"mark" state. The start bit indicates the beginning of the serial data or
character bits. The parity bit is inserted for transmission and tested for
reception if parity is enabled in the SMD register. The stop bit flags
the end of the serial data. The number of stop bits is programmed into
the SMD register.
Also shown in Figure 10-6 is the format for a break sequence. The
detection of a break sequence is flagged in the Serial Status register.
The Serial Command register can be programmed to transmit the
break sequence.
Marking
Start
Bit
7or 8 Data Bits
Asynchronous Data Format
Optional
Parity Bit
1 or 2
Stop
Bits
Marking
Start
Bit
Optional
Parity
Bit
1 or 2
Stop
Bits7 or 8 Data Bits
Break Sequence Format
Figure 10–6. SCU Serial Data Format.
10-12