36 lines
825 B
C
36 lines
825 B
C
#include "platform.h"
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#define KBD_STATUS_OR_KEY ((unsigned char *)0xC000)
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#define KBD_CLEAR_CURRENT_KEY ((unsigned char *)0xC010)
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#define KEY_READY_MASK 0x80
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#define KEY_VALUE_MASK 0x7F
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// Returns non-zero if a key is ready to be read.
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int keyboard_test(void)
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{
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return *KBD_STATUS_OR_KEY & KEY_READY_MASK;
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}
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// Clears current key, sets up next one for test or get
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void keyboard_clear(void)
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{
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unsigned char clear_key;
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// On 6502, a write cycle READS AND THEN WRITES, so just read the
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// "latch next key" strobe.
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clear_key = *KBD_CLEAR_CURRENT_KEY;
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}
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// Wait until a key is ready and then return it without high bit set
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unsigned char keyboard_get(void)
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{
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unsigned char key;
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while(!((key = *KBD_STATUS_OR_KEY) & KEY_READY_MASK));
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keyboard_clear();
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return key & KEY_VALUE_MASK;
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}
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