NuBus-ESP32/Documentation/index.html
2022-02-05 21:03:27 -05:00

94 lines
3.8 KiB
HTML

<html>
<head>
<title>Garrett's Workshop - NuBus-ESP32 Documentation</title>
<style type="text/css">
ul {
margin-top: 0;
}
h3 {
margin-bottom: 0;
}
h2, h4 {
margin-bottom: 3px;
}
h3 + h4 {
margin-top:6px;
}
p {
margin-top:0;
}
ul li {
padding-top: 3px;
}
ul li sup {
line-height: 0;
}
</style>
<script src="https://cdnjs.cloudflare.com/ajax/libs/wavedrom/2.6.8/skins/default.js" type="text/javascript"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/wavedrom/2.6.8/wavedrom.min.js" type="text/javascript"></script>
</head>
<body onload="WaveDrom.ProcessAll()">
<h1>Garrett's Workshop - NuBus-ESP32 Documentation</h1>
<h3>0. NuBus Transfer Acknowledgement</h3>
<script type="WaveDrom">
{signal: [
{name: 'CLK', wave: '101..01..01..01..0', period: 0.5, phase: 0.15},
{name: '/START', wave: '1x0x1....', period: 1, phase: 0.15},
{name: 'TM[1:0]', wave: 'x.2z.x0xz', period: 1, phase: 0.15},
{name: '/ACK', wave: '1....x0xu', period: 1, phase: 0.15},
{name: 'ACK-2', wave: '0..1.0....', period: 1, phase: 0.50},
{name: 'ACK-1', wave: '0....1.0..', period: 1, phase: 0.50},
{name: 'ACK', wave: '0....1.0.', period: 1, phase: 0.00},
]}
</script>
<p>
Here we show the desired cycle termination behavior on the NuBus. To be begin a transfer, a the Mac (or other NuBus master) drives /START low and puts valid data on the address bus and TM[1:0] transfer. <br/>
Notice how the NuBus clock has a 75% duty cycle. All signal transitions occur after the rising edge of CLK and all data is latched at the falling edge of CLK. The 75% duty cycle gives extra propagation delay and setup tiem after the clock rises before data is to be latched at the falling edge. <br/>
TM[1] high means write. TM[1] low means read. TM[0] and A[1:0] indicate the operation size and are not relevant for this application. <br/>
At each falling edge, NuBus slave devices check AD[31:28] and /START. If AD[31:28] matches the slave's card ID and /START is low, the card is supposed to recognize that a NuBus cycle has begun with the card as its target. <br/>
Once the slave device has completed the read/write operation, it responds with /ACK low and TM[1:0] high, indicating a successful transfer. Other values of TM[1:0] can be used to signal a bus error or retry condition. We aren't using those features. <br/>
</p>
<h3>1. Address Latch</h3>
<script type="WaveDrom">
{signal: [
{name: 'CLK', wave: '101..01..01..01..0', period: 0.5, phase: 0.15},
{name: '/START', wave: '1x0x1....', period: 1, phase: 0.15},
{name: 'TM[1:0]', wave: 'x.2z.x1xz', period: 1, phase: 0.15},
{name: 'AD[31:0] (RD)', wave: 'x.2z.x2z.', period: 1, phase: 0.15},
{name: 'AD[31:0] (WR)', wave: 'x.2x2..z.', period: 1, phase: 0.15},
{name: 'ACLK', wave: '0..1.0...', period: 1, phase: 0.50},
{name: 'LA[21:0], LTM[1:0]',wave: '2..2.....', period: 1, phase: 0.35},
{name: '/ACK', wave: '1....x0xu', period: 1, phase: 0.15},
{name: 'ACK-2', wave: '0..1.0...', period: 1, phase: 0.50},
{name: 'ACK-1', wave: '0....1.0.', period: 1, phase: 0.50},
{name: 'ACK', wave: '0....1.0.', period: 1, phase: 0.00},
]}
</script>
<p>
</p>
<h3>2. Read/Write Signals</h3>
<script type="WaveDrom">
{signal: [
{name: 'CLK', wave: '101..01..01..01..0', period: 0.5, phase: 0.15},
{name: '/START', wave: '1x0x1....', period: 1, phase: 0.15},
{name: 'TM[1:0]', wave: 'x.2z.x1xz', period: 1, phase: 0.15},
{name: '/ACK', wave: '1....x0xu', period: 1, phase: 0.15},
{name: '/ROMOE, /REGOE', wave: '1.........0....1...', period: 0.5, phase: 0.50},
{name: '/ROMWE, /REGWE', wave: '1....0.1.', period: 1, phase: 0.50},
{name: 'ACK-2', wave: '0..1.0...', period: 1, phase: 0.50},
{name: 'ACK-1', wave: '0....1.0.', period: 1, phase: 0.50},
{name: 'ACK', wave: '0....1.0.', period: 1, phase: 0.00},
]}
</script>
<p>
</p>
</body>
</html>