MA28155 Datasheet, PDF (14/20 Pages) Dynex Semiconductor – Radiation Hard Programmable Peripheral Interface

MA28155
Special Mode Combination Considerations.
There are several combinations of modes when not all of
the bits in port C are used for control or status. The remaining
bits can be used as follows:
If programmmed as inputs-
All input lines can be accessed during normal port C
read.
If programmed as outputs
Bits in C upper (PC7-PC4) must be individually
accessed using a bit set/reset function.
Bits in C lower (PC3-PC0) can be accessed using the bit
set/reset function or bits PC2-PC0 may also be accessed as a
trio by writing into port C.
Reading Port C Status.
In Mode 0 Port C transfers data from or to the peripheral
device, When the MA28155 is programmed to function in
Modes 1 or 2 Port C generates or accepts handshaking signals
with the peripheral device, Reading the contents of Port C
allows the programmer to test or verify the status of each
peripheral device and change the program flow accordingly.
There is no special instruction to read the Status
Information from Port C. A normal read operation of Port C is
executed to perform this function.
Figure 18a: Mode 1 Input Configuration
OBF_AN
OBF_BN
Figure 18b: Mode 1 Output Configuration
OBF_AN
14/20
Figure 18c: Mode 2