Signal Description
MOTOROLA
MC68307 USER’S MANUAL
2-13
2.9.2 Timer 2 Input (TIN2/PB7)
This bidirectional signal can be programmed as a clock input that causes events to occur in
timer/counter channel 2, either causing a clock to the event counter or providing a trigger to
the timer value capture logic. When programmed as general-purpose input/output, this sig-
nal functions as bit 7 of port B.
2.9.3 Timer 1 Output (TOUT1/PA3)
This bidirectional signal can be programmed to toggle or pulse low for one system clock
duration when timer/counter channel 1 reaches a reference value. When programmed as
general-purpose I/O, this signal functions as bit 3 of port A.
2.9.4 Timer 2 Output (TOUT2/PA4)
This bidirectional signal can be programmed to toggle or pulse low for one system clock
duration when timer/counter channel 2 reaches a reference value. When programmed as
general-purpose I/O, this signal functions as bit 4 of port A.
2.10 INTERRUPT REQUEST INPUTS
These pins can be programmed to be either prioritized interrupt request lines or port B gen-
eral-purpose input/output lines.
2.10.1 Interrupt Inputs (INT1–INT8/PB8–PB15)
These eight bidirectional signals may be configured as general-purpose parallel I/O ports
with interrupt capability. Each of the pins can be configured either as an input or an output.
When configured as an input, each pin can generate a separate, maskable interrupt on a
high-to-low transition, which is latched internally. The interrupt request level (IPL) can be
programmed individually for each pin, and each causes a unique vector to be fetched during
the subsequent interrupt processing.
2.10.2 Non-Maskable Interrupt Input (IRQ7)
IRQ7 is the highest priority interrupt available to the EC000 core, it is a nonmaskable inter-
rupt (IPL=7) and cannot be superseded by any other interrupt request. This is an active-low
input.
2.11 USE OF PULLUP RESISTORS
In general, pins that are input-only or output-only do not require external pullup resistors.
However, see the notes on low power consumption in the following paragraphs.
The open-drain bidirectional signals (HALT, RESET, DTACK, SCL/PB0, SDA/PB1) always
require pullup resistors.
The bus control outputs (AS, UDS, LDS, R/W) three-state at reset during bus arbitration and
low-power sleep mode. They need pullups only if they are decoded for use in the user’s
design or if minimum power consumption is required, otherwise they can be left as
unconnected outputs.