Z8F1680SH020SG Datasheet, PDF (302/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
277
21.1.2. Option Bit Types
This section describes the User, Trim and Calibration option bit types.
21.1.2.1. 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.
21.1.2.2. Trim Option Bits
The trim option bits are contained in the Flash memory information page. These bits are
factory programmed values required to optimize the operation of onboard analog circuitry
and cannot be permanently altered by the user. Program Memory can 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 00H and 1FH into 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 00H and 1FH into the
Trim Bit Address Register. The next read from the Trim Bit Data Register returns the
working value of the target trim data byte.
Note: The trim address ranges from information address 20-3F only. The remainder of the
information page is not accessible via the trim bit address and data registers.
21.1.2.3. 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 area of the address space as defined in the Flash Information Area section
on page 21.
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
PS025015-1212
PRELIMINARY
Flash Option Bits