W78IRD2 Datasheet, PDF (58/76 Pages) Winbond – 8-BIT MICROCONTROLLER

W78IRD2
16. H/W REBOOT MODE (BOOT FROM LDROM)
By default, the W78IRD2 boots up from the AP Flash EPROM after a power-on reset. Sometimes, this
is not desirable. H/W REBOOT mode forces the W78IRD2 to use the LD Flash EPROM instead and
execute in-system programming procedures. Enter H/W REBOOT mode using these settings.
H/W REBOOT MODE
P4.3
P2.7
P2.6
OPTION BIT
MODE
X
L
L
Bit4 = L
H/W REBOOT
L
X
X
Bit5 = L
H/W REBOOT
This might be implemented by connecting pins P2.6 and P2.7 to switches or jumpers. For example, in
a CD-ROM system, P2.6 and P2.7 might be connected to the PLAY and EJECT buttons on the panel.
If the user wants to enter H/W REBOOT mode, the user can press these two buttons at the same time
and then turn on the power to force the W78IRD2 to enter H/W REBOOT mode. After the power-on,
releasing both buttons finishes the in-system programming procedure.
This mode can be accidentally activated, so be careful with the values of pins P2, P3, ALE, EA and
PSEN at reset.
P2.7
P2.6
The Reset Timing For Entering H/W
REBOOT Mode 1
Hi-Z
Hi-Z
RST
P4.3
10us
20ms
H/W REBOOT Mode 2
Hi-Z
RST
10us
20ms
Figure 16-1
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