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Section 7 ROM
7.1
Overview
The H8/3150 series has an on-chip ROM (H8/3152: 24 kbytes; H8/3153: 32 kbytes; H8/3155 and
H8/3156: 16 kbytes; H8/3158: 46 kbytes). The ROM is connected to the CPU by a 16-bit data bus.
Both byte data and word data are accessed in two states, enabling rapid data transfer.
If word access is performed at an odd address in ROM, the word at the preceding even address is
accessed. Normally an even address should be specified for word data.
7.1.1
Block Diagram
Figures 7.1 to 7.4 show block diagrams of the ROM.
H'5FFE
H'5FFF
H'0002
H'0003
H'0000
H'0001
Even addresses
Odd addresses
Internal data bus
(upper 8 bits)
Internal data bus
(lower 8 bits)
On-chip ROM
(24 kbytes)
Figure 7.1 ROM Block Diagram (H8/3152)