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Copies in a few more hardware notes.

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Thomas Harte 2019-10-02 19:18:09 -04:00
parent 2638a901d9
commit 6c99048211
1 changed files with 44 additions and 0 deletions
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44
Components/8530/z8530.cpp
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@ -216,8 +216,52 @@ void z8530::Channel::write(bool data, uint8_t pointer, uint8_t value) {
case 0x1: // Write register 1 — Transmit/Receive Interrupt and Data Transfer Mode Definition.
interrupt_mask_ = value;
/*
b7 = 0 => Wait/Request output is inactive; 1 => output is informative.
b6 = Wait/request output is for...
0 => wait: floating when inactive, low if CPU is attempting to transfer data the SCC isn't yet ready for.
1 => request: high if inactive, low if SCC is ready to transfer data.
b5 = 1 => wait/request is relative to read buffer; 0 => relative to write buffer.
b4/b3:
00 = disable receive interrupt
01 = interrupt on first character or special condition
10 = interrupt on all characters and special conditions
11 = interrupt only upon special conditions.
b2 = 1 => parity error is a special condition; 0 => it isn't.
b1 = 1 => transmit buffer empty interrupt is enabled; 0 => it isn't.
b0 = 1 => external interrupt is enabled; 0 => it isn't.
*/
LOG("[SCC] Interrupt mask: " << PADHEX(2) << int(value));
break;
case 0x3: { // Write register 3 — Receive Parameters and Control.
// Get bit count.
int receive_bit_count = 8;
switch(value >> 6) {
default: receive_bit_count = 5; break;
case 1: receive_bit_count = 7; break;
case 2: receive_bit_count = 6; break;
case 3: receive_bit_count = 8; break;
}
LOG("[SCC] Receive bit count: " << receive_bit_count);
/*
b7,b6:
00 = 5 receive bits per character
01 = 7 bits
10 = 6 bits
11 = 8 bits
b5 = 1 => DCD and CTS outputs are set automatically; 0 => they're inputs to read register 0.
(DCD is ignored in local loopback; CTS is ignored in both auto echo and local loopback).
b4: enter hunt mode (if set to 1, presumably?)
b3 = 1 => enable receiver CRC generation; 0 => don't.
*/
} break;
case 0x4: // Write register 4 — Transmit/Receive Miscellaneous Parameters and Modes.
// Bits 0 and 1 select parity mode.
if(!(value&1)) {