Bus Master Interface; 16-Bit Data Registers - Hitachi H8S/2646 Hardware Manual

17.3

Bus Master Interface

17.3.1

16-Bit Data Registers

PWCYR1/2, PWBFR1A/C/E/G, and PWBFR2A/B/C/D are 16-bit registers. These registers are
linked to the bus master by a 16-bit data bus, and can be read or written in 16-bit units. They
cannot be read by 8-bit access; 16-bit access must always be used.
Internal data bus
H
Bus
L
master
Figure 17-8 16-Bit Register Access Operation (Bus Master ↔ PWCYR1 (16 Bits))
17.3.2 8-Bit Data Registers
PWCR1/2, PWOCR1/2, and PWPR1/2 are 8-bit registers that can be read and written to in 8-bit
units. These registers are linked to the bus master by a 16-bit data bus, and can be read or written
by 16-bit access; in this case, the lower 8 bits will always be read as H'FF.
Internal data bus
H
Bus
L
master
Figure 17-9 8-Bit Register Access Operation (Bus Master ↔ PWCR1 (Upper 8 Bits))
626
Bus
interface
Bus
interface
PWCYR1
PWCR1
Module
data bus
Module
data bus