μ
PSD323X
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Reset Flash.
The Reset Flash instruction con-
sists of one WRITE cycle (see Table 85). It can
also be optionally preceded by the standard two
WRITE decoding cycles (writing AAh to 555h and
55h to AAAh). It must be executed after:
– Reading theFlash Protection Statusor FlashID
– An Error condition has occurred (and the device
has set the Error Flag Bit (DQ5) to ’1’ during a
Flash memory Program or Erase cycle.
The Reset Flash instruction puts the Flash memo-
ry backinto normal READ Mode. If an Errorcondi-
tion has occurred (and the device has set the Error
Flag Bit (DQ5) to ’1’ the Flash memory is put back
into normal READ Mode within 25
μ
s of the Reset
Flash instruction having been issued. The Reset
Flash instruction is ignored when it is issued dur-
ing a Program or Bulk Erase cycle of the Flash
memory. The Reset Flash instruction aborts any
on-going Sector Erase cycle, and returns the
Flash memory to the normal READ Mode within
25
μ
s.
Reset (RESET) Signal.
A pulse on Reset (RE-
SET) aborts any cycle that is in progress, and re-
sets the Flash memory to the READ Mode. When
the reset occurs during a Program or Erase cycle,
the Flashmemory takes up to 25
μ
s to return to the
READ Mode. It is recommended that the Reset
(RESET) pulse (except for Power-on RESET, as
described on page 140) be at least 25
μ
s so that
the Flash memory is always ready for the MCU to
retreive the bootstrap instructions after the reset
cycle is complete.
SRAM
The SRAM is enabled when SRAM Select (RS0)
from the DPLD is High. SRAM Select (RS0) can
contain up to two product terms, allowing flexible
memory mapping.
The SRAM can be backed up using an external
battery. The external battery should be connected
to Voltage Stand-by (V
STBY
, PC2). If you have an
external battery connected to the
μ
PSD3200, the
contents of the SRAM are retained in the event of
a power loss. The contents of the SRAM are re-
tained so longas thebattery voltage remains at 2V
or greater. If thesupply voltage falls below the bat-
tery voltage, an internal power switch-over to the
battery occurs.
PC4 can be configured as an output that indicates
when power is being drawn from the external bat-
tery. Battery-on Indicator (V
BATON
, PC4) is High
with thesupply voltage falls below the battery volt-
age and the battery on Voltage Stand-by (V
STBY
,
PC2) is supplying power to the internal SRAM.
SRAM Select (RS0), Voltage Stand-by (V
STBY
,
PC2) and Battery-on Indicator (V
BATON
, PC4) are
all configured using PSDsoft Express Configura-
tion.
Sector Select and SRAM Select
Sector Select (FS0-FS7, CSBOOT0-CSBOOT3)
and SRAM Select (RS0) are all outputs of the
DPLD. They are setup by writing equations for
them in PSDsoft Express. The following rules ap-
ply to the equations for these signals:
1. Primary Flash memory and secondary Flash
memory Sector Select signals must notbe larg-
er than the physical sector size.
2. Any primary Flash memory sector must not be
mapped in the same memory space as another
Flash memory sector.
3. A secondary Flash memory sector must not be
mapped in the same memory space as another
secondary Flash memory sector.
4. SRAM, I/O, and Peripheral I/O spaces must not
overlap.
5. A secondary Flash memory sector may overlap
a primary Flash memory sector. In case of over-
lap, priority is given to the secondary Flash
memory sector.
6. SRAM, I/O, and Peripheral I/O spaces may
overlap any other memory sector. Priority is giv-
en to the SRAM, I/O, or Peripheral I/O.