MC68HC711E20CFN2 Freescale Semiconductor, MC68HC711E20CFN2 Datasheet - Page 150

• Manufacturer Part Number: MC68HC711E20CFN2
• Description: IC MCU 20K 2MHZ OTP 52-PLCC
• Manufacturer: Freescale Semiconductor
• Series: HC11r

Specifications of MC68HC711E20CFN2

• Core Processor: HC11
• Core Size: 8-Bit
• Speed: 2MHz
• Connectivity: SCI, SPI
• Peripherals: POR, WDT
• Number Of I /o: 38
• Program Memory Size: 20KB (20K x 8)
• Program Memory Type: OTP
• Eeprom Size: 512 x 8
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 52-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Serial Communications Interface (SCI)
7.6.1 Idle-Line Wakeup
7.6.2 Address-Mark Wakeup
Technical Data
150
To use the receiver wakeup method, establish a software addressing
scheme to allow the transmitting devices to direct a message to
individual receivers or to groups of receivers. This addressing scheme
can take any form as long as all transmitting and receiving devices are
programmed to understand the same scheme. Because the addressing
information is usually the first frame(s) in a message, receivers that are
not part of the current task do not become burdened with the entire set
of addressing frames. All receivers are awake (RWU = 0) when each
message begins. As soon as a receiver determines that the message is
not intended for it, software sets the RWU bit (RWU = 1), which inhibits
further flag setting until the RxD line goes idle at the end of the message.
As soon as an idle line is detected by receiver logic, hardware
automatically clears the RWU bit so that the first frame of the next
message can be received. This type of receiver wakeup requires a
minimum of one idle-line frame time between messages and no idle time
between frames in a message.
The serial characters in this type of wakeup consist of seven (eight if
M = 1) information bits and an MSB, which indicates an address
character (when set to 1, or mark). The first character of each message
is an addressing character (MSB = 1). All receivers in the system
evaluate this character to determine if the remainder of the message is
directed toward this particular receiver. As soon as a receiver
determines that a message is not intended for it, the receiver activates
the RWU function by using a software write to set the RWU bit. Because
setting RWU inhibits receiver-related flags, there is no further software
overhead for the rest of this message.
When the next message begins, its first character has its MSB set, which
automatically clears the RWU bit and enables normal character
reception. The first character whose MSB is set is also the first character
to be received after wakeup because RWU gets cleared before the stop
bit for that frame is serially received. This type of wakeup allows
messages to include gaps of idle time, unlike the idle-line method, but
Serial Communications Interface (SCI)
M68HC11E Family — Rev. 3.2
MOTOROLA