Elan Digital Systems Ltd.
12
HD717 USER’S
GUIDE
WR8
xxxxxxxx = xxh
WR9
xx1x1x1x = 2Ah
No vector on INTACK
MIE = ON
*1
Software INTACK mode = ON
*1
Set to on when s/w is ready to
service interrupts from the SCC...see
also HD717 PCR, IPR & IMR for
interrupt enabling / acknowledging,
status and masking.
WR10
xxxxx0xx = x0h
Send Flag on TX underrun
WR11
000010xx = 08h
Set TRxC pin as an INPUT
Select TRxC pin as TX clock
Select RTxC pin as RX clock
RTxC is NOT a crystal osc
NB: The TRxC pin on the SCC is wired
to a logic driver circuit (the output
of the TX clock select MUX on the
card). Therefore it MUST be set to an
input on the SCC if SCS2 is high in
the SCS register.
NB: The sources for the TX and RX
clock can also be set to the BRGen or
DPLL of the SCC. The SCC does not
have to use the external clock
sources. When using DPLL, observe the
maximum data rates (Zilog data sheets)
for the SCC to be able to recover the
clock from the data stream.
See also the HD717 SCS register for
the external clock selection options.
WR12
xxxxxxxx = xxh
WR13
xxxxxxxx = xxh