HD64F3670 Datasheet, PDF (56/323 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

2.6 Basic Bus Cycle
CPU operation is synchronized by a system clock (ø) or a subclock (ø_SUB). The period from a rising
edge of ø or ø_SUB to the next rising edge is called one state. A bus cycle consists of two states or
three states. The cycle differs depending on whether access is to on-chip memory or to on-chip
peripheral modules.
2.6.1 Access to On-Chip Memory (RAM, ROM)
Access to on-chip memory takes place in two states. The data bus width is 16 bits, allowing access
in byte or word size. Figure 2.9 shows the on-chip memory access cycle.
ø or ø_SUB
Internal address bus
Bus cycle
T₁ state
T₂ state
Address
Internal read signal
Internal data bus
(read access)
Read data
Internal write signal
Internal data bus
(write access)
Write data
Figure 2.9 On-Chip Memory Access Cycle
Rev. 2.0, 03/02, page 32 of 298