Attiny85 code on Attiny84 I made OLED timer/watch using Attiny85, but as internal clock isnt accurate i need external crystal. On Attiny85 im short on pins so i am switching to Attiny84 but i have problems to compile/upload same code to Attiny84. Even if i stay on Attiny84 8mhz internal clock as on Attiny85 i still cant compile.
Im using Arduino UNO as ISP.

Error what i have:

WDT_Time.cpp: In function 'void setup_watchdog(uint8_t)':
WDT_Time.cpp:272: error: 'WDTCR' was not declared in this scope
WDTCR |= (1 &lt;&lt; WDCE) | (1 &lt;&lt; WDE);
^
In file included from c:\program files (x86)\arduino\hardware\tools\avr\avr\include\avr\io.h:99:0,
             from c:\program files (x86)\arduino\hardware\tools\avr\avr\include\avr\pgmspace.h:88,
             from C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Arduino.h:28,
             from WDT_Time.cpp:12:
WDT_Time.cpp:276: error: 'PCIE' was not declared in this scope
   sbi(GIMSK, PCIE); // Turn on Pin Change interrupts (Tell Attiny85 we want to use pin change interrupts (can be any pin))
              ^
WDT_Time.cpp:276:3: note: in expansion of macro 'sbi'
   sbi(GIMSK, PCIE); // Turn on Pin Change interrupts (Tell Attiny85 we want to use pin change interrupts (can be any pin))
   ^
WDT_Time.cpp:277: error: 'PCMSK' was not declared in this scope
   sbi(PCMSK, PCINT3);
       ^
WDT_Time.cpp:277:3: note: in expansion of macro 'sbi'
   sbi(PCMSK, PCINT3);
   ^
'WDTCR' was not declared in this scope
There are slight differences between registers, register names and registers bit names:


WDTCR is named WDTCSR
PCIE doesn't exist in GIMSK as there are two IO ports, so there are two pin change channels: PCIE0 and PCIE1
and PCMSK is similar to PCIE. There'll be two of them too.


Basically you have to look into both datasheets and compare what you are using and check if it's correct.