Sega 32X Manual download pdf (Page 76)

1.11. 32X Block Access by Z80

Blocks that can be directly accessed

Z80 is laoded as the MEGA Drive sound CPU. Event when 32X is mapping in the 68000

address space, 68000 memory area can access each 8000h by switching banks similar to

when using the Mega Drive unit. See Table 4.1 "32X Buffer Register List" in section 4.1

for individual buffer registers.

Competition with other CPUs

Access competition to the 32X block of 68000 and SH2 applies to both Z80 and SH2.

See section 4.2 for more information.

Frame Buffer Access

Frame buffer can be written in bytes but data 0 byte write is ignored (Same for write from

both 68000 and SH2).

1 2 ... 71 72 73 74 75 76 77 78 79 80 81 ... 101 102

Hardware Manual 1
Doc. #MAR-32-R4-072294 1
Terminology 4
Contents 5
1. Introduction to 32X 7
New Screen Offered 8
New Sounds Offered 8
High-Speed Microprocessor 8
Development Language 8
2. Configuration 9
Figure 2.1 32X Block Diagram 10
MEGA Drive I/F Component 11
32X Cartridge Component 11
SH2 Component 11
SDRAM Component 12
Frame Buffer Component 12
VDP Component 12
Color Palette Component 13
PWM Component 13
3. Functions 14
MEGA Drive Memory Map 15
ROM Access when using the 32X 16
Access to the 32X VDP 16
SH2 Memory Map 17
Figure 3.2 SH2 Memory Map 17
Cache Area Access 18
Cartridge ROM Access 18
32X VDP Access 18
1.5. Registers 19
Using the 32X 21
Interrupt issued for SH2 22
Switches ROM Cartridge Bank 22
(Acces : Word) 24
(Access : Word) 24
(Acces: Byte/Word) 25
(Access : Byte/Word) 25
(Access: Byte/Word) 26
[SH2 side] 28
(Access : Byte/Word) 28
PWM Interrupt Clear Register 30
(Access : Word) 32
VDP Registers 36
1.6. VDP 39
Figure 3.4 32X VDP Mapping 41
Switching Frame Buffers 42
Figure 3.7 Over Write Image 45
Line Table Format 47
Figure 3.8 Line Table Format 47
Priority 48
Figure 3.9 Priority 48
Direct Color Mode 49
Figure 3.10 Direct Color Mode 49
Packed Pixel Mode 50
Figure 3.11 Packed Pixel Mode 50
Screen Shift Control 51
Run Length Mode 52
Figure 3.13 Run Length Mode 52
FILL Function 53
Before Fill 53
After Fill 53
Mega Drive Master Clock Cycle 54
68000 Clock Cycle 54
SH2 Clock Cycle 54
VDP Register Latch Timing 56
1.7. PWM 57
Master and Slave 62
Note 2 : See next page 63
Figure 3.25 SH2 Address 64
V: valid bit 64
Purge (Cache Initialization) 66
CPU Write 67
Flow of Data 67
Master-Slave Communication 68
Communication Port 69
CMD Interrupt 69
4. 32X Block Access 72
SH2 Address Space 73
Cache-through Access 74
VDP Access Competition 74
ROM Access Competition 74
Competition with other CPUs 76
Frame Buffer Access 76
32X Mode and Cartridge ROM 77
Frame Buffer 77
VDP Register 78
System Register 78
Boot ROM 78
SDRAM Access Time 78
5. Other 79
Initial Program 83
Security 83
6. Annexes 88
1.16. Master Boot ROM 89
1.17. Initial program 95

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Sega 32X Manual Page 76

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