General Control Register 1 [NOT SBC VARIANTS]
This register is used to define the default expansion bus (STEbus or
PC/104), the function of the STEbus arbiter and whether the board
is STEbus default master, potential master or slave.
The default address of this register under the monitor software is
I/O FC06h. It is repeated at FC07h.
Signal Description
The SARB1 and SARB0 signals have the following function:
User Links and LEDS
The TARGET386EX has two user links and two user LEDs and a link
that determines whether the monitor software or application code is
run on power-up or reset. These links and LEDs are connected
directly to the 386EX processors integral parallel port pins as
follows:
Links
J539 TARGET386EX
2192-08270-000-000
Section 4. Using the TARGET386EX
Page 22
Reference
LK17
LK18
LK19
386EX Parallel Port Connection
Port P1 bit 6
Port P1 bit 7
Port P3 bit 6
(this link is used for run mode selection by the monitor)
Bit 7
Unused bits
6
5
4
3
INTCO
M
2
DEFSTE
1
SARB1
0
SARB0
Signal
INTCOM
DEFSTE
SARB1
SARB0
Reset State
0
0
0
0
R/W
R/W
R/W
R/W
R/W
Description
Interrupt compatibility . If set /EN3-0 (see
interrupt Assignments) are permanently low.
Off-board cycles routed to PC/104 (0) or STEbus (1)
STEbus arbiter and bus requester control.
STEbus arbiter and bus requester control.
SARB1
SARB0
Function
0
0
1
1
0
1
0
1
STEbus slave. STEbus arbiter disabled, DPR,
mailbox and interrupt out enabled.
STEbus potential master on BUSRQ0*. STEbus
arbiter disabled , DPR and mailbox disabled and
interrupt out enabled.
STEbus potential master on BUSRQ1*. STEbus
arbiter disabled , DPR and mailbox disabled and
interrupt out enabled.
STEbus default master. STEbus arbiter enabled. DPR
and mailbox disabled and interrupt out enabled.
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