+
+
+/*****************************************************************************/
+/* (W) AUDC1-4 register values */
+/*****************************************************************************/
+
+/* Meaningful values for the distortion bits.
+** The first process is to divide the clock value by the frequency,
+** then mask the output using the polys in the order below;
+** finally, the result is divided by two.
+*/
+#define AUDC_POLYS_5_17 0x00
+#define AUDC_POLYS_5 0x20 /* Same as 0x60 */
+#define AUDC_POLYS_5_4 0x40
+#define AUDC_POLYS_17 0x80
+#define AUDC_POLYS_NONE 0xA0 /* Same as 0xE0 */
+#define AUDC_POLYS_4 0xC0
+
+/* When set, the volume value in AUDC1-4 bits 0-3 is sent directly to the speaker;
+** it is not modulated with the frequency specified in the AUDF1-4 registers.
+** (See "De Re Atari" Chapter 7: Sound)
+*/
+#define AUDC_VOLUME_ONLY 0x10
+
+
+/*****************************************************************************/
+/* (W) AUDCTL register values */
+/*****************************************************************************/
+
+#define AUDCTL_CLOCKBASE_15HZ 0x01 /* Switch main clock base from 64 KHz to 15 KHz */
+#define AUDCTL_HIGHPASS_CHAN2 0x02 /* Insert high pass filter into channel two, clocked by channel four */
+#define AUDCTL_HIGHPASS_CHAN1 0x04 /* Insert high pass filter into channel one, clocked by channel two */
+#define AUDCTL_JOIN_CHAN34 0x08 /* Join channels four and three (16 bit) */
+#define AUDCTL_JOIN_CHAN12 0x10 /* Join channels two and one (16 bit) */
+#define AUDCTL_CLOCK_CHAN3_179MHZ 0x20 /* Clock channel three with 1.79 MHz */
+#define AUDCTL_CLOCK_CHAN1_179MHZ 0x40 /* Clock channel one with 1.79 MHz */
+#define AUDCTL_9BIT_POLY 0x80 /* Makes the 17 bit poly counter into nine bit poly (see also: RANDOM) */
+
+
+/*****************************************************************************/
+/* (W) IRQEN register values */
+/*****************************************************************************/
+
+#define IRQEN_TIMER_1 0x01 /* The POKEY timer one interrupt is enabled */
+#define IRQEN_TIMER_2 0x02 /* The POKEY timer two interrupt is enabled */
+#define IRQEN_TIMER_4 0x04 /* The POKEY timer four interrupt is enabled */
+#define IRQEN_SERIAL_TRANS_FINISHED 0x08 /* The serial out transmission finished interrupt is enabled */
+#define IRQEN_SERIAL_OUT_DATA_REQUIRED 0x10 /* The serial output data required interrupt is enabled */
+#define IRQEN_SERIAL_IN_DATA_READY 0x20 /* The serial input data ready interrupt is enabled. */
+#define IRQEN_OTHER_KEY 0x40 /* The "other key" interrupt is enabled */
+#define IRQEN_BREAK_KEY 0x80 /* The BREAK key is enabled */
+
+
+/*****************************************************************************/
+/* (W) SKCTL register values */
+/*****************************************************************************/
+
+#define SKCTL_KEYBOARD_DEBOUNCE 0x01 /* Enable keyboard debounce circuits */
+#define SKCTL_KEYBOARD_SCANNING 0x02 /* Enable keyboard scanning circuit */
+
+/* Fast pot scan
+** The pot scan counter completes its sequence in two TV line times instead of
+** one frame time (228 scan lines). Not as accurate as the normal pot scan
+*/
+#define SKCTL_FAST_POT_SCAN 0x04
+
+/* POKEY two-tone mode
+** Serial output is transmitted as a two-tone signal rather than a logic true/false.
+*/
+#define SKCTL_TWO_TONE_MODE 0x08
+
+/* Force break (serial output to zero) */
+#define SKCTL_FORCE_BREAK 0x80
+
+
+/* Bits 4, 5, and 6 of SKCTL set Serial Mode Control: */
+
+/* Trans. & Receive rates set by external clock; Also internal clock phase reset to zero. */
+#define SKCTL_SER_MODE_TX_EXT_RX_EXT 0x00
+
+/* Trans. rate set by external clock; Receive asynch. (ch. 4) (CH3 and CH4). */
+#define SKCTL_SER_MODE_TX_EXT_RX_ASYNC 0x10
+
+/* Trans. & Receive rates set by Chan. 4; Chan. 4 output on Bi-Direct. clock line. */
+#define SKCTL_SER_MODE_TX_CH4_RX_CH4_BIDIR 0x20
+
+/* N.B.: Bit combination 0,1,1 not useful */
+
+/* Trans. rate set by Chan. 4; Receive rate set by external clock. */
+#define SKCTL_SER_MODE_TX_CH4_RX_EXT 0x40
+
+/* N.B.: Bit combination 1,0,1 not useful */
+
+/* Trans. rate set by Chan. 2; Receive rate set by Chan. 4; Chan. 4 out on Bi-Direct. clock line. */
+#define SKCTL_SER_MODE_TX_CH2_RX_CH4_BIDIR 0x60
+
+/* Trans. rate set by Chan. 2; Receive asynch. (chan 3 & 4); Bi-Direct. clock not used (tri-state condition). */
+#define SKCTL_SER_MODE_TX_CH4_RX_ASYNC 0x70
+
+
+/*****************************************************************************/
+/* Define a structure with the POKEY register offsets for read (R) */
+/*****************************************************************************/
+