Epson S5U1C33001H1400 Manual page 30

communication between the S5U1C33001H and the target system may be disconnected after the
second reset.
Design the target system so that switch bounce does not occur and the system starts up only once.
Furthermore, if the reset is applied with either the power or the oscillator in an unstable state (for
example, if the reset is applied within the first few ms after the power is turned on), the S1C33xxx
chip operation will also be unstable. In this case the system will not enter debug mode and
communication between the S5U1C33001H and the target system will not be possible. Apply the reset
only after an adequate stabilization time has elapsed.
Refer to the "S1C33xxx Technical Manual" for more information on the reset operation.
• If the S5U1C33001H is turned on after the target system power is turned on:
When the S5U1C33001H is turned on, it issues a forcible break to the free-running target system. The
S1C33xxx chip enters debug mode and starts communication with the S5U1C33001H. If a boot
program was not loaded into ROM, the S1C33xxx chip cannot respond to the forced break since the
S1C33xxx chip is in the runaway state, so communication is impossible. Load a boot program that
operates correctly into boot ROM so that the target system will not be in the runaway state.
• If the initial connection operation fails
In this case, add a reset switch to the target system and start the system in the following sequence:
(1) Turn the target system on
(2) Hold down the reset switch on the target system and turn the S5U1C33001H on
(3) Release the reset switch to clear the reset state.
This will allow the system to operate reliably. This is because this sequence reliably reproduces the
conditions in the "If the S5U1C33001H is turned on after the target system power is turned on" item
above. If it is not possible to connect, install a reset switch on the target system.
We recommend adding the reset switch at the system design stage.
• RESET/WRITE switch on the S5U1C33001H
Besides turning power on and off, the S5U1C33001H can be reset using the on-board RESET/WRITE
switch.
Also the RESET/WRITE switch changes the signal output from the TARGET_RESET pin in the
target system power supply connector (see next section).
S1C33 Family In-Circuit Debugger
S5U1C33001H1400 Manual (Rev. 0.20)
6. START-UP METHOD (POWER-ON SEQUENCE)
EPSON
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