On-Board Memo~Y Control Port - ADC Super Net S-100 Technical Manual

07
=
MSB, 00 = LSB
l=bank on, 0=bank off
Memory Bank 0000H-3FFFH
Memory Bank 4000H-7FFFH
Memory Bank 80Q0H-BFFFH
Menory Bank C000H-FFFFH
Oon't care
PROM enable=0, Disable=l
Power on jump re5et=1
Oon't care
4.9 On-Board Memory Control port
16 Write On-Board Memory Control Port
This port controls the onboard memory managment circuit,
prom enable and disable and power on jump reset circuits.
port write :
The four low order bits 00,01,02 and
D3
switch the on board memory
in 16k banks corresponding to address 0000h-3FFFh,4000H-7FFFH,
8000H-BFFFH and C000-FFFFH on and off. When a particular bank is
switched off, external 5100 memory can be accessed in that
banks address range. This feature allows external memory to be
added to the system for multi-user operating systems.
Bit D5 of this port switches the on-board EPROM on and off.
The onboard EPROM occupfes address F000H-FFFFH. The EPROM
is switched on automatically during
~eset
or power on, the
EPROM contains
510
and FOC initialization code along with ~
simple debugger and floppy disk cold start loader. After
the operating sys~em is loaded the EPROM can be turned off
~
50 that the ram at address F000H-FFFFH can be accessed.
Bit 06 reset the power on jump circuit. Bit 06 must be set
high after a reset or power on situationbefore ram can
be accessed.
+----+----~----+----+----~----+----+----+
!
07
!
06 1 05 1 04 1 03 1 02
!
Dl ! DO !
+----+----+----~----+----~----+----+----+
! ! ! 1 ! 1 ! !
! 1 1 1 1
+--
1 1 1
+-------
! !
+------------
!
!
1
+----~------------
! !
+----------------------
!
+---------------------------
+--------------------------------
~-------------------------------------
14