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Type
Symbol
Clock
OSC2
ø
Operating mode
MD2 to MD0
control
RES
System control
STBY
FWE
Interrupts
NMI
IRQ5 to IRQ0 Input
Address bus
A23 to A0
Data bus
D15 to D0
AS
Bus control
RD
I/O
Name and Function
Input
Subclock: Connects to a 32 kHz crystal oscillator.
See section 21, Clock Pulse Generator, for typical
connection diagrams for a crystal oscillator.
Output
System clock: Supplies the system clock to an external
device.
Input
Mode pins: These pins set the operating mode.
The relation between the settings of pins MD2 to MD0
and the operating mode is shown below. These pins
should not be changed while the H8S/2646 Series is
operating.
MD2
MD1
0
0
1
1
0
1
Input
Reset input: When this pin is driven low, the chip is
reset.
Input
Standby: When this pin is driven low, a transition is
made to hardware standby mode.
Input
Flash write enable: Pin for flash memory use (in
planning stage).
Input
Nonmaskable interrupt: Requests a nonmaskable
interrupt. When this pin is not used, it should be fixed
high.
Interrupt request 5 to 0: These pins request a
maskable interrupt.
Output
Address bus: These pins output an address.
I/O
Data bus: These pins constitute a bidirectional data
bus.
Output
Address strobe: When this pin is low, it indicates that
address output on the address bus is enabled.
Output
Read: When this pin is low, it indicates that the
external address space can be read.
MD0
Operating Mode
0
—
1
—
0
—
1
—
0
Mode 4
1
Mode 5
0
Mode 6
1
Mode 7
21
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