Eshs

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Newer EEPROMs may be fast enough.  W27C512 may be a commonly available EEPROM.
Newer EEPROMs may be fast enough.  W27C512 may be a commonly available EEPROM.
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=== Audio ===
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Sampled from pin 1 of the audio connector on the Esh PCB (CN1).
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[[File:esh_audio_buzz.png]]

Revision as of 23:02, 7 October 2020

Contents

Esh's Aurunmilla

Memory Map

Address Range Description
0x0000-0x1FFF ROM H8
0x2000-0x3FFF ROM F8
0x4000-053FFF ROM E8
0x6000-073FFF ROM D8
0x8000-0x9FFF ROM C8
0xA000-0xDFFF Not connected
0xE000-0xE7FF CPU RAM (B8)
0xF000-0xF7FF Video RAM (F3)

Z80 Port Map

Address Range Direction Description
0xF0 In Control panel input. Only lower 6 data bits are used. Active low.
Bit Description
0 COIN 1
1 COIN 2
2 START 1
3 START 2
4 TEST
0xF1 In Control panel input. Only lower 6 data bits are used. Active low.
Bit Description
0 UP
1 DOWN
2 LEFT
3 RIGHT
4 ACTION 1
5 ACTION 2
0xF2 In Control panel input. Only lower 6 data bits are used.
0xF3 In Control panel input. Only lower 6 data bits are used.
0xF4 In/Out LD-V1000 data. Writing queues a command to be sent on the next command strobe. Reading reads the most recent byte received during last the status strobe.
0xF5 Out Misc value.
Bit Description
0 Not connected
1 is audio (1 = audio signal comes from a vertical counter (VA3), 0 = audio signal is low).
2,3 Bit 2 and 3 deal with whether to show the laserdisc image or not. If bit 3 is high, A7 of the RGB prom is also high, laserdisc video is suppressed, and bit 2 is ignored. If bit 2 is high (and bit 3 is low) A7 of the RGB prom is low, and laserdisc video is suppressed.
4-7 Bits 4-7 indirectly map to A8 of the RGB PROM. They are selectable via bits 6 and 7 of the tile attribute (video memory 0xF400-0xF7FF). Although the hardware applies no further restrictions on use, the Esh program will constantly cycle each of these bits. Bit 4 doesn't cycle at all and is always high. Bit 5 cycles at about 15 Hz. Bit 6 cycles at about 7.5 Hz. Bit 7 cycles at about 4.3 Hz. The game uses this for variable blink speed.
0xF8 Out 0 disables start 1 button lamp. 1 enables.
0xF9 Out Start 2 button lamp. 0 disables, 1 enables.
0xFA Out 0 disables action button lamp. 1 enables.
0xFB Out 0 disables joystick lamp. 1 enables.
0xFC Out Not connected
0xFD Out Not connected
0xFE Out 0 holds IRQ' line high (disabled) by forcing a latch to be clear. 1 stops forcing latch to be clear, which allows IRQs to set the latch.
0xFF Out 0 holds NMI' line high (disabled) by forcing a latch to be clear. 1 stops forcing latch to be clear, which allows NMIs to set the latch.

Z80 Interrupts

NMI: Caused by LD-V1000 status strobe going low (becoming active)

IRQ: Caused by D2 output (pin 10) on vertical PROM (C6) transitioning from 0 to 1. This ends up being 60 Hz (vsync).

Video RAM Structure

Screen is divided into 32x32 tiles. The first tile is the top left.

0xF000-0xF3FF contain which tile to show.

0xF400-0xF7FF contain tile attributes. For example, 0xF400 would have attributes about the tile index at 0xF000.

Bit Description
0-3 Which color palette to use for the tile.
5-6 Not used
6-7 Blink frequency. 0: no blinking, 1: blink at about 15 Hz, 2: blink at about 7.5 Hz, 3: blink at about 4.3 Hz ; The blink frequency is controlled by the Z80 program, and is not a hardware restriction.

PROM replacements

H and V PROMs are MB7052. MB7052 may compatible with 82s129 proms, but in my tests, 82S129's overheat and fail to perform. One option is http://callanbrown.com/index.php/flep-prom-replacement-adapters

RGB PROM is MB7124. MB7124 are compatible with 82s147 proms. Haven't found any other replacement yet.

Newer EEPROMs may be fast enough. W27C512 may be a commonly available EEPROM.

Audio

Sampled from pin 1 of the audio connector on the Esh PCB (CN1).

Esh audio buzz.png

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