Zilog Z16C35 - Manual (Page 91)

ISCC
User Manual
UM011002-0808
85
If the data is written immediately after the Go Active On Poll bit has been set, the ISCC
will only insert one flag after the EOP is changed into a flag. If the data is not written until
after the receiver enters the Hunt mode, the flags will be transmitted until the data is writ-
ten. If only one frame is to be transmitted on the loop in response to an EOP, the processor
must set the Go Active on Poll bit to “0” before the last data is written to the transmitter. In
this case the transmitter will close the frame with a single flag, and then revert to the one-
bit delay. The Loop Sending bit in RR10 is set to “0” when the closing Flag has been sent.
If more than one frame is to be transmitted, the Go Active On Poll bit should not be set to
“0” until the last frame is being sent. If this bit is not set to “0” before the end of a frame,
the transmitter will send Flags until either more data is written to the transmitter, or until
the Go Active On Poll bit is set to “0”. Note that the state of the Abort/Flag on Underrun
and Mark/Flag idle bits in WR10 are ignored by the ISCC in SDLC Loop mode.
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