X68C75 Datasheet, PDF (13/26 Pages) Xicor Inc. – Port Expander and E2 Memory

X68C75 SLIC^® E²
the interrupt is enabled, an external interrupt will be
asserted at the completion of the internal write cycle.
The interrupt is cleared by setting EOW to “0”.
USING A PORT IN BIDIRECTIONAL MODE
In order to use a port in bidirectional mode, it has to be
configured as an open drain output port. Small pull-up
resistors are required on all port output pins. Bit positions
in the port data register corresponding to port inputs
should contain “1”. The inputs are then read by access-
ing PPR. Data is not latched into the device, so the inputs
must stay valid throughout the read cycle. The port
strobe pin is configured as an output and cannot be used
as port latch clock input.
SLIC FUNCTIONS (68HC11 Specific SLIC)
The resident SLIC E² has designated memory spaces
allocated for its use. The user’s application code should
avoid using these areas as part of its code segment,
otherwise it will overwrite the SLIC E². Version 3.0 of the
X68C75 SLIC E² occupies 192 bytes in the upper
memory bank, FF00-FFC0H, and 336 bytes in the lower
bank’s address range E000-E14FH. Prior to download-
ing code, assemble and link the source files using the
above address information. Use memory space taken
up by the SLIC E² as a run-time data storage, if there is
no further need to modify the X68C75 SLIC E² content.
The current version of the SLIC E² configures the 68HC11
serial port to the variable baud rate mode. It sets a timer
prescalar value for a system clock rate of 8MHz. For
other clock rates, the end user must recalculate timer 1
reload value for 9600 baud rate and write it into the
Figure 13.
E000
E150
SLIC
User’s Program/Data
FF00
FFC0
FFFF
SLIC
ISR & Reset Vectors
2899 ILL F15
X68C75 location E024H. The XSLIC software, a PC
based communication driver, automates changing of
the default parameters when using its SETUP option
menu. The boot-firmware (SLIC) residing on the X68C75
contains a lookup table which can be accessed from the
subroutine (EXEC_FUNC), located at location E120H.
Two bytes are used per table entry. The EXEC_FUNC
input requirements are as follows:
B = Contains a function number from the following
function table.
The table entry at location (E14E-E14FH) is reserved for
user’s application code. This function will be executed
on power-up if the SLIC receives any characters other
than those for the RESET (ASCII ‘R’), or ID (ASCII ‘X’)
commands. This table entry can be changed to point to
other code responsible for power-up initialization. This
method is preferred to changing the reset vector, since
the SLIC code can still be invoked upon power-up.
Other functions available through the EXEC_FUNC
calls are as follows:
Table 2.
FUNCTION NO.
DESCRIPTION
0 - PROC_PROG
1 - PROC_BPR
2 - RESET
3 - PROC_VER
4 - DUMMY
5 - INIT_UART
6 - PROG_PG
7 - SEND_CHAR
8 - GET_CHAR
9 - SDP_HI_PLANE
10- SDP_LO_PLANE
11- USER_CODE
Download and program a
page
Program BPR
Start execution from
location E000H
Download and verify a page
Command not recognized
Initialize UART parameters
to default
Program a page
Send a character to the
UART
Read a character from the
RAM receive buffer (40H-5FH)
Generate SDP off sequence
for upper plane
Generate SDP off sequence
for lower plane
Execute user’s code
2899 PGM T03.2
For detailed information about the listed functions, in-
cluding their input requirements, refer to the SLIC soft-
ware specification document.
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