Skip to main content
Renesas Electronics America - Knowledgebase

Read and write access on Timer Fs 8-bit counters TCFH and TCFL in 16-bit ?

Latest Updated:03/18/2009


How do I reliably make read and write accesses to Timer Fs 8-bit counters TCFH and TCFL when in 16-bit mode ?


Read and write accesses to this register must be performed 16-bits at a time using two consecutive byte-size MOV instructions and the upper byte must be accessed before the lower byte. i.e MOV.B  @HFFB8:8 R6H , MOV.B  @HFFB9:8 R6LD. Data will not be transferred correctly if only the upper byte or only the lower byte is accessed. Correct operation can be achieved using assembler or an intrinsic function call EEPMOV. The EEPMOV instruction also masks interrupts which stops an interrupt occuring during the above instructions ensure that interrupts can not occur during the byte-size MOV instructions. For more details please see section 9.4.3 of the hardware manual regarding the CPU Interface for Timer F.
Suitable Products
H8/300H Super Low Power
H8/300L Super Low Power
H8 Super Low Power