SDA55XX Datasheet, PDF (67/230 Pages) Infineon Technologies AG – Preliminary & Confidential

Preliminary & Confidential
SDA 55xx
Microcontroller
It is not allowed to drive Port 3.6 to logic low level while reset state changes from the
active to inactive state otherwise a special test mode is activated.
Secondary functions can be selected individually and independently for the pins of port 1
and 3. Further information on port 1's secondary functions is given in chapter ‘Pulse
Width Modulation Unit’. P3 generates the secondary control signals automatically as
long as the pin corresponding to the appropriate signal is programmed as an input, i. e.
if the corresponding bit latch in the P3 special function register contains a ‘one’.
Read Modify-Write Feature
‘Read-modify-write’ commands are instructions that read a value, possibly change it, and
then rewrite it to the latch. When the destination operand is a port or a port bit, these
instructions read the latch rather than the pin. The read-modify-write instructions are
listed in table 8.
The read-modify-write instructions are directed to the latch rather than the pin in order to
avoid a possible misinterpretation of the voltage level at the pin. For example, a port bit
might be used to drive the base of a transistor. When a ‘one’ is written to the bit, the
transistor is turned on.
If the CPU then reads the same port bit at the pin rather than the latch, it will read the
base voltage of the transistor and interpret it as a 0. Reading the latch rather than the pin
will return the correct value of ‘one’.
Timer/Counter 0 Mode 3: Two 8-Bit Counters
Figure 8
Read-Modify-Write Instructions
Mnemonic
Description
Example
ANL
ORL
XRL
JBC
CPL
INC
DEC
DJNZ
MOV PX.Y, C¹⁾
CLR PX.Y¹⁾
SET PX.Y¹⁾
logical AND
logical OR
logical EX – OR
jump if bit = 1 and clear bit
complement bit
increment
decrement
decrement and jump if not zero
move carry bit to bit Y of Port X
clear bit Y of Port X
set bit Y of Port X
ANL P1, A
ORL P2, A
XRL P3, A
JBC P1.1, LABEL
CPL P3.0
INC P1
DEC P1
DJNZ P3, LABEL
MOV P1.7, C
CLR P2.6
SET P3.5
1) _{The instruction reads the port byte (all 8 bits), modifies the addressed bit, then writes the new byte back to}
the latch
Semiconductor Group
67
User’s Manual July 99