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ibmpc: Fix comments

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tmk 2020-03-02 01:21:04 +09:00
parent b7412f6228
commit 0b1fbeb135
1 changed files with 31 additions and 27 deletions
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46
tmk_core/protocol/ibmpc.c
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@ -229,49 +229,53 @@ ISR(IBMPC_INT_VECT)
if (dbit) isr_state |= 0x8000; if (dbit) isr_state |= 0x8000;
// isr_state: state of receiving data from keyboard // isr_state: state of receiving data from keyboard
// This is initialized with 0x8000 before start receiving data and MSB '1' of //
// the initial value is marker bit to discrimitate between protocols. // This should be initialized with 0x8000 before receiving data and
// the MSB '*1' works as marker to discrimitate between protocols.
// It stores sampled bit at MSB after right shift on each clock falling edge. // It stores sampled bit at MSB after right shift on each clock falling edge.
// //
// XT protocol has two variants of signaling; XT_IBM and XT_Clone.
// XT_IBM uses two start bits 0 and 1 while XT_Clone uses just start bit 1.
// https://github.com/tmk/tmk_keyboard/wiki/IBM-PC-XT-Keyboard-Protocol
//
// 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 // 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
// ----------------------------------------------------- // -----------------------------------------------------
// Initial: *1 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 with MSB marker *1 // *1 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 Initial state(0x8000)
// XT_Type-1: b7 b6 b5 b4 b3 b2 b1 b0 | 1 0 *1 0 0 0 0 0 start bit 0 and 1 **
// XT_Type-2: b7 b6 b5 b4 b3 b2 b1 b0 | 1 *1 0 0 0 0 0 0 start bit 1
// AT: st pr b7 b6 b5 b4 b3 b2 | b1 b0 0 *1 0 0 0 0 start bit 0
// AT**: pr b7 b6 b5 b4 b3 b2 b1 | b0 0 *1 0 0 0 0 0 before stop bit **
// //
// x x x x x x x x | 0 0 0 0 0 0 0 0 midway(0-7 bits received) // x x x x x x x x | 0 0 0 0 0 0 0 0 midway(0-7 bits received)
// x x x x x x x x | *1 0 0 0 0 0 0 0 midway(8 bits received) // x x x x x x x x | *1 0 0 0 0 0 0 0 midway(8 bits received)
// x x x x x x x x | 0 *1 0 0 0 0 0 0 XT_Type1-midway or AT-midway // b6 b5 b4 b3 b2 b1 b0 1 | 0 *1 0 0 0 0 0 0 XT_IBM-midway ^1
// x x x x x x x x | 1 *1 0 0 0 0 0 0 XT_Type2-done // b7 b6 b5 b4 b3 b2 b1 b0 | 0 *1 0 0 0 0 0 0 AT-midway ^1
// x x x x x x x x | 0 0 *1 0 0 0 0 0 AT-midway[b0=0] // b7 b6 b5 b4 b3 b2 b1 b0 | 1 *1 0 0 0 0 0 0 XT_Clone-done
// x x x x x x x x | 1 0 *1 0 0 0 0 0 XT_Type1-done or AT-midway[b0=1] // pr b7 b6 b5 b4 b3 b2 b1 | 0 0 *1 0 0 0 0 0 AT-midway[b0=0]
// b7 b6 b5 b4 b3 b2 b1 b0 | 1 0 *1 0 0 0 0 0 XT_IBM-done ^2
// pr b7 b6 b5 b4 b3 b2 b1 | 1 0 *1 0 0 0 0 0 AT-midway[b0=1] ^2
// x x x x x x x x | x 1 1 0 0 0 0 0 illegal // x x x x x x x x | x 1 1 0 0 0 0 0 illegal
// x x x x x x x x | x x 0 1 0 0 0 0 AT-done // st pr b7 b6 b5 b4 b3 b2 | b1 b0 0 *1 0 0 0 0 AT-done
// x x x x x x x x | x x 1 1 0 0 0 0 illegal // x x x x x x x x | x x 1 *1 0 0 0 0 illegal
// other states than above illegal // all other states than above illegal
// //
// **: AT takes same state as XT_Type1-done(1010 000) in case that AT b0 is 1, // ^1: AT and XT_IBM takes same state.
// to discriminate between the two protocol we will have to wait a while for AT stop bit. // ^2: AT and XT_IBM takes same state in case that AT b0 is 1,
// we have to check AT stop bit to discriminate between the two protocol.
switch (isr_state & 0xFF) { switch (isr_state & 0xFF) {
case 0b00000000: case 0b00000000:
case 0b10000000: case 0b10000000:
case 0b01000000: case 0b01000000: // ^1
case 0b00100000: case 0b00100000:
// midway // midway
goto NEXT; goto NEXT;
break; break;
case 0b11000000: case 0b11000000:
// XT_Type2-done // XT_Clone-done
recv_data = recv_data<<8; recv_data = recv_data<<8;
recv_data |= (isr_state>>8) & 0xFF; recv_data |= (isr_state>>8) & 0xFF;
goto DONE; goto DONE;
break; break;
case 0b10100000: case 0b10100000: // ^2
{ {
uint8_t us = 100; uint8_t us = 100;
// wait for rising and falling edge of AT stop bit // wait for rising and falling edge of AT stop bit to discriminate between XT and AT
while (!(IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT)) && us) { wait_us(1); us--; } while (!(IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT)) && us) { wait_us(1); us--; }
while ( IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT) && us) { wait_us(1); us--; } while ( IBMPC_CLOCK_PIN&(1<<IBMPC_CLOCK_BIT) && us) { wait_us(1); us--; }
@ -279,7 +283,7 @@ ISR(IBMPC_INT_VECT)
// found stop bit: AT-midway - process the stop bit in next ISR // found stop bit: AT-midway - process the stop bit in next ISR
goto NEXT; goto NEXT;
} else { } else {
// no stop bit: XT_Type1-done // no stop bit: XT_IBM-done
recv_data = recv_data<<8; recv_data = recv_data<<8;
recv_data |= (isr_state>>8) & 0xFF; recv_data |= (isr_state>>8) & 0xFF;
goto DONE; goto DONE;