User’s Manual
C166S V1 SubSystem
Asynchronous/Synchronous Serial Interface (ASC)
User’s Manual
10-11
V 1.6, 2001-08
Figure 10-6
Asynchronous 9-Bit Frames
In wake-up mode, received frames are transferred to the receive buffer register only if
the 9th bit (the wake-up bit) is 1. If this bit is 0, no receive interrupt request will be
activated and no data will be transferred.
This feature may be used to control communication in a multi-processor system:
When the master processor wants to transmit a block of data to one of several slaves, it
first sends out an address byte to identify the target slave. An address byte differs from
a data byte in that the additional 9th bit is a 1 for an address byte, but is a 0 for a data
byte; so, no slave will be interrupted by a data ’byte’. An address ’byte’ will interrupt all
slaves (operating in 8-bit data + wake-up bit mode), so each slave can examine the eight
LSBs of the received character (the address). The addressed slave will switch to 9-bit
data mode (such as by clearing bit CON_M.0), to enable it to also receive the data bytes
that will be coming (having the wake-up bit cleared). The slaves not being addressed
remain in 8-bit data + wake-up bit mode, ignoring the following data bytes.
10.3.1.2
Asynchronous Transmission
Asynchronous transmission begins at the next overflow of the divide-by-16 baudrate
timer (transition of the baudrate clock f
BR
), if bit CON_R is set and data has been loaded
into TBUF. The transmitted data frame consists of three basic elements:
– Start bit
– Data field (eight or nine bits, LSB first, including a parity bit, if selected)
– Delimiter (one or two stop bits)
Data transmission is double-buffered. When the transmitter is idle, the transmit data
loaded in the transmit buffer register TBUF is immediately moved to the transmit shift
register, thus freeing the transmit buffer for the next data to be sent. This is indicated by
the transmit Buffer interrupt request line TBIR being activated. TBUF may now be loaded
with the next data, while transmission of the previous data continues.
Bit 9
D7
D0
LSB
D1
D2
D3
D4
D5
D6
Start
Bit
9 Data Bits
11-/12-Bit UART Frame
(1st)
Stop
Bit
0
1
1
(2nd)
Stop
Bit
&21B0
%
Bit 9 = Data Bit D8
&21B0
%
Bit 9 = Wake-up Bit
&21B0
%
Bit 9 = Parity Bit
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
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