80C154 TEMIC Semiconductors, 80C154 Datasheet - Page 7

• Manufacturer Part Number: 80C154
• Description: CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller
• Manufacturer: TEMIC Semiconductors

Rev.F (14 Jan. 97)
Stop Clock Mode
Due to static design, the TEMIC 83C154 clock speed can
be reduced until 0 MHz without any data loss in memory
or registers. This mode allows step by step utilization, and
permits to reduce system power consumption by bringing
the clock frequency down to any value. At 0 MHz, the
power consumption is the same as in the Power Down
Mode.
I/O Ports
The I/O drives for P1, P2, P3 of the 83C154 are
impedance programmable. The I/O buffers for Ports 1, 2
and 3 are implemented as shown in figure 4.
When the port latch contains 0, all pFETS in figure 4 are
off while the nFET is turned on. When the port latch
makes a 0-to-1 transition, the nFET turns off. The strong
pullup pFET, T1, turns on for two oscillator periods,
pulling the output high very rapidly. As the output line is
drawn high, pFET T3 turns on through the inverter to
supply the IOH source current. This inverter and T3 form
a latch which holds the 1 and is supported by T2. When
Port 2 is used as an address port, for access to external
program of data memory, any address bit that contains a
1 will have his strong pullup turned on for the entire
duration of the external memory access.
When an I/O pin on Ports 1, 2, or 3 is used as an input, the
user should be aware that the external circuit must sink
current during the logical 1-to-0 transition. The
MATRA MHS
Table 1. Status of the external pins during idle and power down modes.
Figure 4. I/O Buffers in the 83C154 (Ports 1, 2, 3).
Power Down
Power Down
MODE
Idle
Idle
PROGRAM MEMORY
External
External
Internal
Internal
ALE
1
1
0
0
www.DataSheet4U.com
PSEN
1
1
0
0
maximum sink current is specified as ITL under the D.C.
Specifications.
approximately 2 V, T3 turns off to save ICC current. Note,
when returning to a logical 1, T2 is the only internal
pullup that is on. This will result in a slow rise time if the
user’s circuit does not force the input line high.
The input impedance of Port 1, 2, 2 are programmable
through the register IOCON. The ALF bit (IOCON0) set
all of the Port 1, 2, 3 floating when a Power Down mode
occurs. The P1HZ, P2HZ, P3HZ bits (IOCON1,
IOCON2, IOCON3) set respectively the Ports P1, P2, P3
in floating state. The IZC (IOCON4) allows to choose
input impedance of all ports (P1, P2, P3). When IZC = 0,
T2 and T3 pullup of I/O ports are active ; the internal input
impedance is approximately 10 K. When IZC = 1 only T2
pull-up is active. The T3 pull-up is turned off by IZC. The
internal impedance is approximately 100 K.
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output respectively,
of an inverting amplifier which is configured for use as an
on-chip oscillator, as shown in figure 5. Either a quartz
crystal or ceramic resonator may be used.
To drive the device from an external clock source,
XTAL1 should be driven while XTAL2 is left
unconnected as shown in figure 6. There are no
requirements on the duty cycle of the external clock
signal, since the input to the internal clocking circuitry is
through a divide-by-two flip-flop, but minimum and
maximum high and low times specified on the Data Sheet
must be observed.
Figure 5. Crystal Oscillator.
Port Data
Port Data
PORT0
Floating
Floating
80C154/83C154
When
Port Data
Port Data
Port Data
Port Data
PORT1
the
Port Data
Port Data
Port Data
PORT2
Address
input
goes
Port Data
Port Data
Port Data
Port Data
PORT3
below
7