X88C75 Datasheet, PDF (13/27 Pages) Xicor Inc. – Port Expander and E2 Memory

X88C75 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 posi-
tions in the Port Data Register corresponding to port
inputs should contain “1”. The inputs are then read by
accessing 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 (80C51 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
X88C75 SLIC E² occupies 256 bytes in the upper
memory bank, starting at address 1F00H, and 288 bytes
in the lower bank’s address range 30H-14FH. Prior to
downloading 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 X88C75
SLIC E² content.
Figure 13.
0000H
0030H
ISR & Reset Vectors
0150H
SLIC
01F00H
User’s Program/Data
SLIC
2887 ILL F17
The current version of the SLIC E² configures the 80C51
serial port to the variable baud rate mode. It sets a timer
1 reload value for a system clock rate of 11.059MHz. For
other clock rates end user must recalculate timer 1
reload value for 9600 baud rate and write it into the
X88C75 location 00E8H. 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 X88C75
contains a lookup table which can be accessed from the
subroutine (EXEC_SUB), located at location 0126H.
Two bytes are used per table entry. The EXEC_SUB
input requirements are as follows:
R0 = Contains a Function Number from the following
Function Table.
The table entry at location (014E-014FH) 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. The table entry can be changed to point to
other code responsible for power-up initialization. This is
preferred method than changing the reset vector, since
the SLIC code can still be invoked upon power-up.
Other functions available through the EXEC_SUB calls
is as follows:
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 0000H
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
2887 PGM T03.1
For detailed information about the listed functions, in-
cluding their input requirements, refer to the SLIC soft-
ware specification document.
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