SYSCR1 selects the functions of four of the port 1 pins. It also selects the input edge of the NMI
pin.
At a reset and in the hardware standby mode, SYSCR1 is initialized to H'87. It is not initialized in
the software standby mode.
Bit 7—Reserved:
This bit cannot be modified and is always read as 1.
Bit 6—Interrupt Request 1 Enable (IRQ
1
E):
This bit selects the function of pin P1
6
.
Bit 6
IRQ
1
E
0
1
Description
P1
6
functions as an input/output pin.
P1
6
functions as the IRQ
1
input pin, regardless of the value set in P1
6
DDR. (However,
the CPU can still read the pin status by reading P1DR.)
(Initial value)
Bit 5—Interrupt Request 0 Enable (IRQ
0
E):
This bit selects the function of pin P1
5
.
Bit 5
IRQ
0
E
0
1
Description
P1
5
functions as an input/output pin.
P1
5
functions as the IRQ
0
input pin, regardless of the value set in P1
5
DDR. (However,
the CPU can still read the pin status by reading P1DR.)
(Initial value)
Bit 4—Nonmaskable Interrupt Edge (NMIEG):
This bit selects the input edge of the NMI pin.
It is not related to port 0.
Bit 4
NMIEG
0
Description
A nonmaskable interrupt is generated on the falling edge
of the input at the NMI pin.
A nonmaskable interrupt is generated on the rising edge
of the input at the NMI pin.
(Initial value)
1
Bit 3—Bus Release Enable (BRLE):
This bit selects the functions of pins P1
2
and P1
3
. It is
valid only in the expanded modes (modes 1, 2, 3, and 4). In the single-chip mode, pins P1
2
and
P1
3
function as input/output pins regardless of the value of the BRLE bit.
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