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EF6805U3FND View Datasheet(PDF) - STMicroelectronics

Part NameDescriptionManufacturer
EF6805U3FND 8-BIT MICROCOMPUTER UNIT ST-Microelectronics
STMicroelectronics ST-Microelectronics
EF6805U3FND Datasheet PDF : 31 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
EF6805U3
Control.
0 - Cleared under Program Control.
TCR3 - Timer prescaler reset bit : A read of TCR3
TCR5 TCR4
0
0
0
1
1
0
1
1
Result
Internal Clock to Timer
AND of Internal Clock and TIMER
Pin to Timer
Input to timer disabled.
TIMER Pin to Timer
always indicates a zero.
1 - Set on external Reset, Power-On-Reset or
under Program Control.
0 - Cleared under Program Control
Figure 10 : Timer Block Diagram.
TCR2 , TCR1, and TCR0 - Prescaler address
bits :
1 - All set on external Reset, Power-On-Reset
or under Program Control.
0 - Cleared under Program Control.
Figure 9 : Timer Control Register (TCR).
TCR2 TCR1 TCR0 Result
0 0 0 +1
0 0 1 +2
0 1 0 +4
0 1 1 +8
TCR2 TCR1 TCR0 Result
1 0 0 + 16
1 0 1 + 32
1 1 0 + 64
1 1 1 + 128
Notes : 1. Prescaler and 8-bit counter are clocked on the failing edge of the internal clock (AS) or external input.
2. Counter is written to during dat strobe (DS) and counts down continuously.
SELF-CHECK - The self-check capability of the
EF6805U3 MCU provides an internal check to de-
termine if the part is functional. Connect the MCU as
shown in figure 11 and monitor the output of Port C
bit 3 for an oscillation of approximately 7Hz. A 10-
volt level (through a 10k resistor) on the timer input,
pin 8 and pressing then releasing the RESET but-
ton, energizes the ROM-based self-check feature.
The self-check program exercices the RAM, ROM,
TIMER, interrupts, and I/O ports.
Several of the self-check subroutines can be called
by a user program with a JSR or BSR instruction.
They are the RAM, ROM. The timer routine may also
be called if the timer input is the internal 2 clock.
To call those subroutines in customer application,
please contact your local SGS-THOMSON Micro-
electronics sales office in order to obtain the
complete description of the self-check program and
the entrance/exit conditions.
RAM SELF-CHECK SUBROUTINE - The RAM self-
check is called at location $F84 and returns with the
Z bit clear if any error is detected ; otherwise the Z
bit is set. The RAM test causes each byte to count
from 0 up to 0 again with a check after each count.
The RAM test must be called with the stack pointer
at $07F and A = 0. When run, the test checks every
RAM cell except for $07F and $07E which are as-
sumed to contain the return address.
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