Interface To Bus Master; 16-Bit Registers; Figure 12.2 16-Bit Register Access Operation [Bus Master ↔ Tcnt (16 Bits)]; Figure 12.3 8-Bit Register Access Operation [Bus Master ↔ Tcr (Upper 8 Bits)] - Renesas H8S/2437 Hardware Manual

12.4

Interface to Bus Master

12.4.1

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 from or written to in 16-bit units.
These registers cannot be read from 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 12.2.
Internal data bus
H
Bus
L
master
Figure 12.2 16-Bit Register Access Operation [Bus Master ↔
12.4.2 8-Bit Registers
Registers other than TCNT and TGR are 8 bits. As the data bus to the bus master is 16 bits wide,
these registers can be read from or written to in 16-bit units. They can also be read from or written
to in 8-bit units.
Examples of 8-bit register access operation are shown in figures 12.3, 12.4, and 12.5.
Internal data bus
H
Bus
L
master
Figure 12.3 8-Bit Register Access Operation [Bus Master ↔
Bus interface
Bus interface
TCNTH TCNTL
↔ TCNT (16 Bits)]
↔ ↔
TCR
↔ TCR (Upper 8 Bits)]
↔ ↔
Rev. 1.00, 09/03, page 325 of 704
Module
data bus
Module
data bus