CHANGES IMPLEMENTED IN THE
                           REVISION 1 MICROPAC  

GENERAL

Pullups have been added to CSIO1 and CSIO2 to keep them from
selecting devices and causing bus contention in the period of
time between reset and the moment they are initialized as chip
selects.  Other features implemented are as follows:

     1) serial port handshake lines have been changed.
     2) redirection of interrupts via jumper.
     3) interrupt polling capability.
     3) hardware support of BUFFALO single stepper.



COMPATIBILITY WITH REV. 0

CN1 and CN2

The handshake lines pins (4 and 6) should be exchanged to make
them the same as REV. 0.


XIRQ

XIRQ now can only accept 1 input at a time, so COM1 Rx and INT0
cannot be connect to it at the same time.  To connect COM1 to
XIRQ, connect JP7 pin 2 (position A jumper removed) to the center
pin of JP10 (JP10 jumper removed).  To connect INT0 to XIRQ,
connect JP7 pin 4 (position B jumper removed) to the center pin
of JP10 (JP10 jumper removed).


IRQ

To restore the original IRQ interrupt capability, there should be
a jumper in position C (only) of JP7 and no jumper in JP10.  Then
connect the pin of JP10 labeled "E" to pin 3 of JP7.







Following are details of the changes.


LCD PORT

The LCD backlight drive selector has been moved to JP9 (described
later).


KEYPAD PORT

Rev. 1 gives access to another row selector, Y5, by including an
access hole just before pin 1 of the connector (the connector is
the same as before).  When using this extra row, the values 10h,
11h, 12h, and 13h will be returned when X1, X2, X3, or X4 are
intersected, respectively.  Also, if using Y5 the value read from
the port should mask off the upper 3 bits instead of the upper 4.


I/O EXPANSION BUS HEADER

HDR1 pins labeled INT0 and INT1 have been changed in REV. 1 so
that they are no longer directly connected to the XIRQ and IRQ
lines, respectively.  This may be done by wire wrapping


DIGITAL I/O HEADER

PX20 is can also be used to poll interrupts.  See the description
of JP 9.



JP7

(Following is a description of JP7 of rev. 0 and rev. 1.

REV. 0 JP7.

Jumper option JP7 provides selection of LCD backlight control. 
If put in the "on" position the backlight is turned on.  If put
in the "PX20" position the MPU's CSGEN/PG6 line controls the
backlight (PX20 is also available on digital I/O header HDR3). 
See the section "DIGITAL I/O HEADER" for more information.

REV. 1 JP7.

This allows connection of 1 to 3 interrupt sources (or none) to
the IRQ interrupt. Putting jumpers in positions A,B, and C will
enable interrupts from COM1 receive, INT0, and the KEYPAD
interface, respectively. Remember that if you put jumpers in more
than one position and your program requires these interrupts to
occur asynchronously, there is a possibility that they may occur
simultaneously and therefore not be detected! Multiple interrupt
sources on IRQ should be used with care.  


JP9. (REV.1 ONLY)

Putting a jumper in position A or B or C of JP9 (only one of
these 3 positions at a time), allows you to poll the selected
interrupt source by using PX20 (port G 6) in input mode.
Positions A,B, and C correspond to the COM1 receive, INT0, and
KEYPAD interface interrupt sources, respectively. 

Positions D and E determine the drive source for the LCD
backlight. You may put a jumper in only one of the two positions
at a time. If PX20 is not being used for the polling function,
you may put a jumper in position D to drive the LCD backlight
with PX20 in the output mode.  Putting a jumper in position E
will turn on the backlighting continuously, leaving PX20 free to
be used for polling or general purpose I/O.

     
JP10. (REV.1 ONLY)

This is included to enable the single-step function of the
BUFFALO monitor.  Putting a jumper in position "SS" enables the
single stepper by connecting XIRQ to OC5/PA3 (through an
inverter).  A jumper in position "E" connects the INT1 pin of
HDR1 to the invertor that feeds XIRQ*.