Zilog Z16C35 - Manual (Page 61)

ISCC
User Manual
UM011002-0808
55
the character boundaries (i.e., achieving synchronization) is with a logic signal that goes
active just as the first character is about to enter the receiver. This method is referred to as
“External Synchronization”.
Figure 4-4 shows the character format for synchronous transmission. For example, bits 1-
8 might be one character and bits 9-13 part of another character; or bit 1 might be part of a
second character, and bits 10-13 part of a third character. The alignment of the received
bytes to the byte assembly is accomplished by defining a synchronization character, com-
monly called a “sync character”.
Figure 4–19. Monosync Data Character Format
Start and stop bits are not required in synchronous modes. All bits are used to transmit
data. This eliminates the “waste” characteristic of asynchronous communication.
4.3.1 Byte Oriented Synchronous Transmit
Once Synchronous mode has been selected, any of three sync character lengths may be
selected:
6-bit
8-bit
16-bit
The 6-bit option Sync character is selected by setting bits 4 and 5 of WR4 to zeros and bit
0 of WR10 to one. Only the least significant six bits of WR6 are transmitted.
The 8-bit sync character is selected by setting bits 4 and 5 of WR4 to zeros and bit 0 of
WR10 to zero. With this option selected, the transmitter sends the contents of WR6 when
it has no data to send.
Monosync and Bisync modes require clocking information to be transmitted along with
the data either by a method of encoding data that contains clocking information, or by a
Modem Clock
Bit
Bit State
Data
LSB
Sync Character Data Character
1 Bit Time
1 2 3 4 5 6 7 8 9 10 11 12 13 . . .
0 1 1 0 1 0 0 0 1 1 0 1 0 1 0 1
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