HC05 datasheet(107/232 Pages) MOTOROLA

107 / 232 page

MC68HC05X16

Rev. 1

MOTOROLA

7-5

SERIAL COMMUNICATIONS INTERFACE

7.5

Data format

Receive data or transmit data is the serial data that is transferred to the internal data bus from the

receive data input pin (RDI) or from the internal bus to the transmit data output pin (TDO). The

non-return-to-zero (NRZ) data format shown in Figure 7-3 is used and must meet the following

criteria:

–

The idle line is brought to a logic one state prior to transmission/reception of

a character.

–

A start bit (logic zero) is used to indicate the start of a frame.

–

The data is transmitted and received least signiﬁcant bit ﬁrst.

–

A stop bit (logic one) is used to indicate the end of a frame. A frame consists

of a start bit, a character of eight or nine data bits, and a stop bit.

–

A break is deﬁned as the transmission or reception of a low (logic zero) for at

least one complete frame time (10 zeros for 8-bit format, 11 zeros for 9-bit).

7.6

Receiver wake-up operation

The receiver logic hardware also supports a receiver wake-up function which is intended for

systems having more than one receiver. With this function a transmitting device directs messages

to an individual receiver or group of receivers by passing addressing information as the initial

byte(s) of each message. The wake-up function allows receivers not addressed to remain in a

dormant state for the remainder of the unwanted message. This eliminates any further software

overhead to service the remaining characters of the unwanted message and thus improves system

performance.

The receiver is placed in wake-up mode by setting the receiver wake-up bit (RWU) in the SCCR2

are inhibited (cannot become set). Note that the idle line detect function is inhibited while the RWU

bit is set. Although RWU may be cleared by a software write to SCCR2, it would be unusual to do

so. Normally RWU is set by software and is cleared automatically in hardware by one of the two

methods described below.

Figure 7-3 Data format

Start

Stop

Control bit M selects

8 or 9 bit data

Start

Idle line

012345678

105

HC05 Datasheet(PDF) 107 Page - Motorola, Inc

HC05 Datasheet(HTML) 107 Page - Motorola, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL