em78p5842 ELAN Microelectronics Corp, em78p5842 Datasheet - Page 18

• Manufacturer Part Number: em78p5842
• Description: 8-bit Micro-controller
• Manufacturer: ELAN Microelectronics Corp

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* This specification is subject to change without notice.
VII.3 Special Purpose Registers
A (Accumulator)
CONT (Control Register)
P70EG
R/W-1
Internal data transfer, or instruction operand holding
It's not an addressable register.
Bit 0 ~ Bit 2 (PSR0 ~ PSR2) : TCC/WDT prescaler bits
Bit 3(PAB) : Prescaler assignment bit
Bit 4(RETBK) : Return value backup control for interrupt routine
Bit 5(TS) : TCC signal source
Bit 6 (INT) : INT enable flag
CONT register is readable (CONTR) and writable (CONTW).
TCC and WDT :
0/1 Î TCC/WDT
0/1 Î disable/enable
When this bit is set to 1, the CPU will store ACC,R3 status and R5 PAGE automatically after an interrupt is
triggered. And it will be restored after instruction RETI. When this bit is set to 0, the user need to store ACC,
R3 and R5 PAGE in user program.
0 Î Internal instruction cycle clock
1 Î IRC output
0 Î interrupt masked by DISI or hardware interrupt
1 Î interrupt enabled by ENI/RETI instructions
Bit 7: Unused. This bit is not allow to used.
There is an 8-bit counter available as prescaler for the TCC or WDT. The prescaler is available for the TCC
only or WDT only at the same time.
An 8 bit counter is available for TCC or WDT determined by the status of the bit 3 (PAB) of the CONT
register.
See the prescaler ratio in CONT register.
Fig.5 depicts the circuit diagram of TCC/WDT.
7
PSR2
0
0
0
0
1
1
1
1
R/W-0
INT
6
PSR1
0
0
1
1
0
0
1
1
R/W-1
TS
5
PSR0
0
1
0
1
0
1
0
1
RETBK
R/W-1
4
TCC rate
1:128
1:256
1:16
1:32
1:64
1:2
1:4
1:8
R/W-1
PAB
3
16
WDT rate
1:128
1:16
1:32
1:64
1:1
1:2
1:4
1:8
R/W-1
PSR2
2
R/W-1
PSR1
1
R/W-1
PSR0
EM785840/5841/5842
0
8-bit Micro-controller
2004/11/10 V1.2