Z85233 Datasheet, PDF (90/317 Pages) Zilog, Inc. – The Zilog SCC Serial Communication Controller

SCC™/ESCC™ User’s Manual
Data Communication Modes
Modem Controls. Up to two modem control signals asso- Initialization. The initialization sequence for the receiver
ciated with the receiver are available in Synchronous in character-oriented mode is WR4 first, to select the
4 ^{modes: /DTR//REQ and /DCD. The /DTR//REQ pin carries mode, then WR10 to modify it if necessary; WR6 and WR7}
the inverted state of the DTR bit (D7) in WR5 unless this to program the sync characters; WR3 and WR5 to select
pin has been programmed to carry a DMA Request on the various options. At this point the other registers are ini-
Transmit signal. The /DCD pin is ordinarily a simple input tialized as necessary. When all this is completed, the re-
to the DCD bit in RR0. However, if the Auto Enables mode ceiver is enabled by setting bit D0 of WR3 to a one. A sum-
is selected by setting D5 of WR3 to 1, this pin becomes an mary is shown in Table 4-8. A detailed example of using
enable for the receiver. Therefore, if Auto Enables is ON the SCC in 16-bit sync mode is available in the application
and the /DCD pin is High, the receiver is disabled; while note “SCC in Binary Synchronous Communications.”
the /DCD pin is Low, the receiver is enabled.
Note that with Auto Enables mode enabled, when /DCD
goes inactive, the receiver stops immediately and the
character being assembled is lost.
UM010901-0601
4-15