Z80 Datasheet, PDF (303/330 Pages) Zilog, Inc. – Z80 CPU PERIPHERALS

Z80 CPU Peripherals
User Manual
283
Sync Character Load Inhibit (D1)
Sync characters preceding the message (leading sync characters) are not
loaded into the receive buffers if this option is selected. Because CRC
calculations are not stopped by sync character stripping, this feature should
be enabled only at the beginning of the message.
Address Search Mode (D2)
If SDLC is selected, no receive interrupts can occur in the Address Search
mode without an address match. Therefore, messages containing addresses
that do not match the programmed address in WR6 or the global (1111
1111) are rejected.
Receiver CRC Enable (D3)
If this bit is set, CRC calculation starts or restarts at the beginning of the last
character transferred from the receive shift register to the buffer stack. This
start or restart occurs regardless of the number of characters in the stack.
For more information about setting this bit, see “SDLC Receive CRC
Checking” (SDLC Receive section) and “CRC Error Checking”
(Synchronous Receive section).
Enter Hunt Phase (D4)
The Z80 SIO automatically enters the Hunt phase after a reset. However, it
can be re-entered if character synchronization is lost (Synchronous mode)
or if the contents of an incoming message are not needed (SDLC mode).
The Hunt phase is reentered by writing a 1 to bit D4. This sets the Sync/
Hunt bit (D4) in RR0.
Auto Enables(D5)
If this mode is selected, DCD and CTS become the receiver and transmitter
enables, respectively. If this bit is not set, DCD and CTS are simply inputs
to their corresponding status bits in RR0.
UM008101-0601
Serial Input/Output