Hitachi H8S/2645, Hardware Manual

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10.3Interface to Bus Master
10.3.1 16-Bit Registers
TCNT and TGR are 16-bit registers. As the data bus to the bus master is 16 bits wide, these
registers can be read and written to in 16-bit units.
These registers cannot be read or written to in 8-bit units; 16-bit access must always be used.
An example of 16-bit register access operation is shown in figure 10-2.
Bus interface
H
Internal data bus
L
Bus
master
Module
data bus
TCNTH TCNTL
Figure 10-2 16-Bit Register Access Operation [Bus Master
↔
TCNT (16 Bits)]
10.3.2 8-Bit Registers
Registers other than TCNT and TGR are 8-bit. As the data bus to the CPU is 16 bits wide, these
registers can be read and written to in 16-bit units. They can also be read and written to in 8-bit
units.