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68901P05 Schematic ( PDF Datasheet ) - STMicroelectronics

Teilenummer 68901P05
Beschreibung MULTI.FUNCTION PERIPHERAL
Hersteller STMicroelectronics
Logo STMicroelectronics Logo 




Gesamt 33 Seiten
68901P05 Datasheet, Funktion
MK68901
MULTI–FUNCTION PERIPHERAL
. 8 INPUT/OUTPUT PINS
Individually programmable direction
. Individual interrupt source capability
- Programmable edge selection
16 SOURCE INTERRUPT CONTROLLER
8 Internal sources
8 External sources
Individual source enable
Individual source masking
Programmable interrupt service modes
- Polling
- Vector generation
. - Optional In-service status
Daisy chaining capability
FOUR TIMERS WITH INDIVIDUALLY PRO-
GRAMMABLE PRESCALING
Two multimode timers
- Delay mode
- Pulse width measurement mode
- Event counter mode
Two delay mode timers
. Independent clock input
Time out output option
SINGLE CHANNEL USART
Full Duplex
Asynchronous to 65 kbps
Byte synchronous to 1 Mbps
Internal/External baud rate generation
DMA handshake signals
.. Modem control
Loop back mode
68000 BUS COMPATIBLE
48 PIN DIP OR 52 PIN PLCC
1
DPIP48
Figure 1 : Pin connections.
PLCC52
DESCRIPTION
The MK68901 MFP (Multi-Function Peripheral) is a
combination of many of the necessary peripheral
functions in a microprocessor system.
Included are :
Eight parallel I/O lines
Interrrupt controller for 16 sources
Four timers
Single channel full duplex USART
The use of the MFP in a system can significantly re-
duce chip count, thereby reducing system cost. The
MFP is completely 68000 bus compatible, and 24 di-
rectly addressable internal registers provide the ne-
MFP
December 1988
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68901P05 Datasheet, Funktion
MK68901
Figure 7 : Vector Register.
Figure 8 : Interrupt Control Registers.
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68901P05 pdf, datenblatt
MK68901
Figure 15 : A Conceptual Circuit of the MFP Timers in the Pulse Width Measurement Mode.
Changing the prescale value with the timer running
can cause the first Time Out pulse to occur at an in-
determinate time, (no less than one nor more than
200 timer clock cycles times the number in the time
constant register), but subsequent Time Out pulses
will then occur at the correct interval.
In addition to the delay mode described above, Ti-
mers A and B can also function in the Pulse Width
Measurement mode or in the Event Count mode. In
either of these two modes, an auxiliary control signal
is required. The auxiliary control input for Timer A is
TAI, and for Timer B,TBI is used. The interrupt chan-
nels associated with 14 and 13 are used for TAI and
TBI, respectively, in Pulse Width mode. See Figure
15.
The pulse width measurement mode functions
much like the delay mode. However, in this mode,
the auxiliary control signal on TAI or TBI acts as an
enable to the timer. When the control signal on TAI
or TBI is inactive, the timer will be stopped. When it
is active,the prescaler andmain counter are allowed
to run. Thus the width of the active pulse on TAI or
TBI is determined by the number of timer counts
which occur while the pulse allows the timer to run.
The active state of the signal on TAI or TBI is de-
pendent upon the associated Interrupt Channel’s
edge bit (GPIP 4 for TAI and GPIP 3 for TBI : see
Active Edge Register in figure 5). If the edge bit as-
V000332
sociated with the TAI or TBI input is a one, it will be
active high ; thus the timer will be allowed to run
when the input is at a high level. If the edge bit is a
zero, the TAI or TBI input will be active low. As pre-
viously stated, the interrupt channel (13 or 14) as-
sociated with the input still functions when the timer
is used in the pulse width measurement mode. How-
ever, if the timer is programmed for the pulse width
measurement mode, the interrupt caused by tran-si-
tions on the associated TAI or TBI input will occur on
the opposite transition.
For example, if the edge bit associated with the TAI
input (AER-GPIP 4) is as one, an interrupt would
normally be generated on the 0-1 transition of the 14
input signal. If the timer associated with this input
(Timer A) is placed in the pulse width measurement
mode, the interrupt will occur on the 1-0 tran-sition
of the TAI signal instead. Because the edge bit
(AER-GPIP 4) is a one, Timer A will be allowed to
count while the input is high. When the TAI input
makes the high to low transition, Timer A will stop,
and it is at this point that the interrupt will occur (as-
suming that the channel is enabled). This allows the
interrupt to signal the CPU that the pulse being mea-
sured has terminated ; thus Timer A may now be
read to determine the pulse width. (Again note that
13 and 14 may still be used for I/O when the timer
is in the pulse width measurement mode). If Timer
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