19.11.18 TC4 Counter Value Low and High byte

The TCNT4L and TCNT4H register pair represents the 16-bit value, TCNT4. The low byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Timer/Counter Registers.

Name: TCNT4L and TCNT4H
Offset: 0xA4
Reset: 0x00
Property: -

Bit 15141312111098 
 TCNT4[15:8] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 
Bit 76543210 
 TCNT4[7:0] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 

Bits 15:0 – TCNT4[15:0] Timer/Counter 4 Counter Value

The two Timer/Counter I/O locations (TCNT4H and TCNT4L, combined TCNT4) give direct access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To ensure that both the high and low bytes are read and written simultaneously when the CPU accesses these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. Refer to Accessing 16-bit Timer/Counter Registers for details.

Modifying the counter (TCNT4) while the counter is running introduces a risk of missing a compare match between TCNT4 and one of the OCR4x Registers.

Writing to the TCNT4 Register blocks (removes) the compare match on the following timer clock for all compare units.