MC68HC05P4A Datasheet, PDF (43/72 Pages) Advanced Analogic Technologies – Microcontrollers

Chapter 10
Self-Check Mode
10.1 Introduction
The self-check program resides at mask ROM (read-only memory) locations $1F00 to $1FEF. This
program is designed to check the part’s functionality with a minimum of support hardware. The computer
operating properly (COP) subsystem is disabled in the self-check mode so that routines that feed the COP
do not exist in the self-check program.
10.2 Functional Description
The self-check mode is entered on the rising edge of RESET if the IRQ pin is driven to double the supply
voltage and the TCAP/PD7 pin is at logic 1. RESET must be held low for 4064 cycles after power-on reset
(POR) or for a time, t_RL, for any other reset. After reset, the input/output (I/O), random-access memory
(RAM), ROM, timer, simple serial input/output port (SIOP), and interrupts are tested. Self-check results
(using light-emitting diodes (LEDs) as monitors) are shown in Table 10-1. It is not recommended that the
user code use any of the self-check code. The self-check code is subject to change at any time to improve
testability or manufacturability.
Figure 10-1 illustrates a self-check circuit.
Table 10-1. Self-Check Results
PC2
PC1
PC0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
Flashing
All others
Note:
0 indicates LED is on; 1 indicates LED is off.
Remarks
Bad I/O
Bad RAM
Bad timer
Bad ROM
Bad serial
Bad interrupt
Good device
Bad device
MC68HC05P4A Data Sheet, Rev. 7.1
Freescale Semiconductor
43