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comparison simple_console.txt @ 3:08b69e3f9f17

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Fleshed out the video hardware design somewhat
author Michael Pavone <pavone@retrodev.com>
date Fri, 25 Mar 2016 09:06:29 -0700
parents 6204c81e2933
children 8170d60f188b
comparison
equal deleted inserted replaced
2:6204c81e2933 3:08b69e3f9f17
81 r0 - r12 : general purpose 81 r0 - r12 : general purpose
82 r13 : technically general purpose, but canonically the stack register 82 r13 : technically general purpose, but canonically the stack register
83 r14 : PC 83 r14 : PC
84 r15 : status register 84 r15 : status register
85 85
86 Special Registers
87 epc - Exception PC - Stores PC value to resume to when entering an exception handler
88 esr - Exception SR - same as above, but for SR
89 eur - Exceptuion User Reg - reg for temporary storage of a reg in a handler, intended to be used for the stack pointer
90 enum - Exception Number - holds the number of the most recent exception
91
86 IO: Ports 92 IO: Ports
87 93
88 0: Controller 1 94 0: Controller 1
89 1: Controller 2 95 1: Controller 2
90 2: Controller 3 96 2: Controller 3
103 9: Channel C/D Vol 109 9: Channel C/D Vol
104 110
105 A: Timer Freq 111 A: Timer Freq
106 B: "Serial" Debug Port 112 B: "Serial" Debug Port
107 113
108 D: Write Pallette Address : Read Vertical Position 114 C: Write Vertical Scroll : Read Vertical Position
109 E: Write Name Table Address : Read Horizontal Position 115 MMMM MCCC CCCC CFFF
110 F: Write Sprite Table Address : Read Status? 116 C = coarse scroll bit
117 F = fine scroll bit
118 M = mask bit
119 controls which bits come directly from register
120 and which bits come from the sum of the register
121 and the current line number
122
123 D: Write Horizontal Scroll : Read Horizontal Position
124 xxxx xxxC CCCC CFFF
125 C = coarse scroll bit
126 F = fine scroll bit
127 x = unused
128 E: Write Dest Address : Read Status
129 F: Write Data : Read Data
130
131
132 Name Table Start Address:
133 0VVV VVVV VHHH HHH0
134
135 V = Coarse scroll bit from vertical scroll value
136 H = Coarse scroll bit from horizontal scroll value
137
138 VDP Memory Map
139 0000 - 7FFF = Pattern/Name Table RAM
140 8000 - FDFF = unused, returns $FFFF
141 FE00 - FEFF = Sprite RAM
142 FF00 - FF7F = Palette RAM
143 FF80 - FFFF = Palette RAM (mirror)
144
145 Another View -
146 MSB determines whether destination is main RAM
147 For MSB 1
148 Next 7 MSB determines which special RAM is the destination
149 Only values of 7E and 7F are valid for these bits at present
150 8 LSB determine offset (1 LSB ignored)
151
152 Writing to Data port puts word into FIFO
153 Offset within memory type is increment when word is pulled from FIFO
154
155 Pattern Format:
156 4bpp in an 8x8 tile arrangement
157
158
159 Sprite Table Entry:
160
161 XXXXXXXX YYYYYYYY
162 IXPVHSNN NNNNNNNN
163
164 S: size -- 0 = 8x8, 1 = 16x16
165 P: Palette selector
166 H: Horizontal flip
167 V: Vertical flip
168 I: Priority
169 N: Name
170 X: X position (left of screen = 16, right of screen = ?)
171 Y: Y position (top of screen = 16, bottom of screen = 240)
172
173
174 Name Table Entry:
175
176 IPPVHxNN NNNNNNNN
177
178 P: Palette selector
179 H: Horizontal flip
180 V: Vertical flip
181 I: Priority
182 N: Name
183 x: Unused, should be set to 0
184
185 26.112 MHZ Clock
186 Dot Clock Divider 4
187 CPU Clock Divider 20 (assuming 1 cycle/instruction, 5 for 4 cycles/instruction)
188 Audio Timer Divider 34
189 Audio Output Divider 544
190
191 Alternatively 13.056 Mhz clock and cut the dividers in half
111 192
112 193
113 194
114 195 H-Counter goes from 0-415 and then wraps back to zero
115 196 V-Counter goes from 0-261 and then wraps back to zero
197 V-Counter increments when H-Counter wraps