Z8 Encore! XP® F08xA Series
Product Specification
139
Option Bit Types
User Option Bits
The user option bits are contained in the first two bytes of program memory. User access
to these bits has been provided because these locations contain application-specific device
configurations. The information contained here is lost when page 0 of the program mem-
ory is erased.
Trim Option Bits
The trim option bits are contained in the information page of the Flash memory. These bits
are factory programmed values required to optimize the operation of onboard analog cir-
cuitry and cannot be permanently altered by the user. Program memory may be erased
without endangering these values. It is possible to alter working values of these bits by
accessing the Trim Bit Address and Data Registers, but these working values are lost after
a power loss.
There are 32 bytes of trim data. To modify one of these values the user code must first
write a value between 00Hand 1FHinto the Trim Bit Address Register. The next write to
the Trim Bit Data register changes the working value of the target trim data byte.
Reading the trim data requires the user code to write a value between 00Hand 1FHinto the
Trim Bit Address Register. The next read from the Trim Bit Data register returns the work-
ing value of the target trim data byte.
The trim address range is from information address 20-3F only. The remainder of the
information page is not accessible through the trim bit address and data registers.
Note:
Calibration Option Bits
The calibration option bits are also contained in the information page. These bits are fac-
tory programmed values intended for use in software correcting the device’s analog per-
formance. To read these values, the user code must employ the LDC instruction to access
the information of the address space, as defined in “Flash Information Area” on page 13.
The following code example shows how to read the calibration data from the flash infor-
mation area.
; get value at info address 60 (FE60h)
ldx FPS, #%80 ; enable access to flash info page
ld R0, #%FE
ld R1, #%60
ldc R2, @RR0 ; R2 now contains the calibration value
PS024705-0405
P R E L I M I N A R Y
Flash Option Bits
ZILOG [ ZILOG, INC. ]
