X68C75 Datasheet, PDF (9/26 Pages) Xicor Inc. – Port Expander and E2 Memory

X68C75 SLIC^® E²
The complemented contents of the SFR map register
and the E² memory map register can be read by the
microcontroller at their corresponding SFR addresses.
The physical memory location of these registers can be
derived by adding the following offset to the SFR base
address:
SFR Map Register
00H
E² Memory Map Register
38H
If the regions specified in the map registers overlap, only
the SFR will be accessible.
Interrupt Status Register (ISR)
The Interrupt Status Register is a volatile register used
to configure the interrupt condition for the I/O ports as
well as to determine the interrupt status of the ports. The
X68C75 ports can generate an interrupt to the microcon-
troller upon the proper transition (as specified in the
configuration register) on either STRA or STRB pins
when the corresponding I/O port is configured as an
input.
The INT flag is set when any of input strobes are toggled
provided that their corresponding interrupt enable bits
(ENA, ENB) are set. The INT flag is cleared when
latched data is read (PDR ) or pending interrupt status
flag (INTA, INTB) in ISR is forced to “0” by the interrupt
service routine. Interrupt service routine should exam-
ine the interrupt status flags (INTA, INTB) and identify
the source of pending interrupt.
The E² memory interrupt status flag (EOW) is another
means to detect the early completion of a write cycle.
When ENEE is enabled, the hardware will set the EOW
flag, and interrupt the microcontroller at the end of an
internal programming cycle. Toggle Bit Polling can be
replaced by the EOW hardware interrupt, which reduces
the software overhead. The EOW flag should be cleared
by software. The interrupt status register bits are mapped
as follows.
Figure 10. Interrupt Status Register
7
6
5
4
3
2
1
0
INT INTA INTB ENA ENB ENEE 0 EOW
Interrupt Flag
“0” = No pending interrupt
“1” = Interrupt request
Port A – Interrupt Status
“0” = No pending interrupt
“1” = Port A latched data when a valid
transition occurred on the STRA
and port A was an input port.
Port B – Interrupt Status
“0” = No pending interrupt
“1” = Port B latched data when a valid
transition occurred on the STRB
and port B was an input port.
Port A – Interrupt Enable
“0” = Mask off interrupt
“1” = Interrupt enabled
EEPROM Interrupt Status
“0” = Programming in progress
“1” = Set by hardware when it completes
programming the previously
written data
EEPROM Interrupt Enable
“0” = Mask off interrupt
“1” = Interrupt enabled
Port B – Interrupt Enable
“0” = Mask off interrupt
“1” = Interrupt enabled
2899 ILL F12.1
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