Avago Technologies LSI53C120 - Manual (Page 26)

2-8 Functional Description
output setup times. The duration is again controlled by the input
signal.
5. This stage is a trailing edge signal filter. When the signal deasserts,
the filter does not permit any signal bounce. The output signal
deasserts at the first deasserted edge of the input signal.
6. The final stage develops pull-up and pull-down signals with drive and
3-state control.
7. A parallel function ensures that bus (transmission line) recovery is
ensured for a specified time after the last signal deassertion on each
signal line.
2.2.5 Control/Data (C/D), Input/Output (I/O), Message (MSG) and
Attention (ATN) Controls
A_SCD/, A_SIO/, A_SMSG/, A_SATN/, B_SCD/, B_SIO/, B_SMSG/ and
B_SATN/ are control signals. The following steps describe the process
regarding these control signals:
1. The LSI53C120 blocks another input signal if one is already being
driven from the source to the load bus.
2. The next stage is a leading edge filter. This ensures that the output
does not switch for a specified time after the leading edge. The
duration of the input signal then determines the duration of the
output.
3. The final stage develops pull-up and pull-down controls for the SCSI
I/O logic, including 3-state controls for the pull-up.
4. A parallel function ensures that bus (transmission line) recovery is
ensured for a specified time after the last signal deassertion on each
signal line.
2.2.6 Differential Direction Controls
B_SDIR(15-0, P0, P1), B_BSYDIR, B_SELDIR, B_CD_DIR, B_IO_DIR,
B_MSGDIR, B_REQDIR, B_ACKDIR, B_ATNDIR and B_RSTDIR are all
differential direction control signals on the B-side of the LSI53C120.
When the B-side is used in SE mode, these signals are not used and
should be left unconnected. When the B-side is used in HVD mode,
these signals control the direction of each external differential transceiver
on the B-side interface.