83:Ports:04 - Revision history

Kalimero: added documentation for bits 5-7

2005-04-28T22:07:17Z

added documentation for bits 5-7

Kalimero: memory mapping

2005-04-28T20:36:00Z

memory mapping

195.56.94.233 at 08:14, 3 April 2005

2005-04-03T08:14:44Z

195.56.94.233 at 08:12, 3 April 2005

2005-04-03T08:12:26Z

195.56.94.233 at 08:12, 3 April 2005

2005-04-03T08:12:05Z

Kalimero: Added memory map info

2005-04-02T11:00:02Z

Added memory map info

Aquanight: Wrong category (83, not 83Plus)

2005-04-02T00:31:53Z

Wrong category (83, not 83Plus)

195.56.243.181 at 14:43, 1 April 2005

2005-04-01T14:43:46Z

Kalimero at 13:24, 30 March 2005

2005-03-30T13:24:30Z

New page

[[Category:83:Ports:By_Address|04 - Timer Interrupt Frequency]] [[Category:83Plus:Ports:By_Name|Timer Interrupt Frequency]]
== Synopsis ==
'''Port Number:''' 04h

'''Function:''' Timer Interrupt Frequency

This port controls the frequency of the hardware timer.

=== Read Values ===
* Bits 0-7: Undocumented. This port is never read by the TIOS.

=== Write Values ===
* Bit 0: Unknown. The calculator crashes when set. Maybe it has more or less the same behaviour as bit 0 of [[83Plus:Ports:04]].
* Bits 1 and 2 control the hardware timer frequency. Setting both 0 sets the timer to the fastest speed, and both 1 is the slowest speed. The normal speed is with both bits 1.
* Bit 3: Unused? Always 0.
* Bit 4: Unused? Always 1.
* Bit 5-7: Unknown, but definitely used.

@@ Line 1: / Line 1: @@
-[[Category:83:Ports:By_Address|04 - Timer Interrupt Frequency / Memory Map]] [[Category:83:Ports:By_Name|Timer Interrupt Frequency / Memory Map]]
+[[Category:83:Ports:By_Address|04 - Timer Interrupt Frequency / Memory Map / Battery Status]] [[Category:83:Ports:By_Name|Timer Interrupt Frequency / Memory Map / Battery Status]]
 == Synopsis ==
 '''Port Number:''' 04h
-'''Function:''' Timer Interrupt Frequency and Memory Map Control
+'''Function:''' Timer Interrupt Frequency, Memory Map Control and Battery Status Checking
-This port controls the frequency of the hardware timer and the memory map mode.
+This port controls the frequency of the hardware timer and the memory map mode. The higher bits of this port control at which voltage level [[83:Ports:14|bit 0 of port 14]] flips.
 === Read Values ===
@@ Line 15: / Line 15: @@
 * Bit 3: Unused? Always 0.
 * Bit 4: Timer frequency multiplier; when this bit is set, all the times are multiplied by 90% (i. e. it's 11.1% faster) compared to when it's reset.
-* Bit 5-7: Unknown, but definitely used.
+* Bit 5: Set this bit to keep the [[83:OS:Hardware Reset|reset circuit]] high even when [[83:Ports:14|bit 0 of port 14]] is 0. The default value for this bit is 0.
 == Comments ==
-To calculate the resulting timer frequency you can use the following formula:
+* The voltages given above are purely indicative and may be highly inaccurate. (until somebody confirms them)
-freq = 1800 * ((out_value & 0x10) ? 1.0 : 0.9) / (3 + ((out_value & 0x06) << 1))
+== Example ==

@@ Line 11: / Line 11: @@
 === Write Values ===
-* Bit 0 reset to select memory map mode 0. In mode 0 the RAM and ROM is mapped to CPU memory as follows:
+* Bit 0 controls the [[83:OS:Memory Mapping|memory mapping mode]]. The default value for this bit is 0.
-** Address 0000h ~ 3FFFh: ROM Page 0
+* Bits 1 and 2 control the hardware timer frequency. Setting both 0 sets the timer to the fastest speed, and both 1 is the slowest speed. The default is with both bits 1.
-** Address 4000h ~ 7FFFh: Swappable (Page selected in [[83:Ports:00]]/[[83:Ports:02]])
-** Address 8000h ~ BFFFh: RAM Page 1
-** Address C000h ~ FFFFh: RAM Page 0
-* Bit 0 set to select memory map mode 1. In mode 1 the RAM and ROM is mapped to CPU memory as follows:
-** Address 0000h ~ 3FFFh: ROM Page 0
-** Address 4000h ~ 7FFFh: RAM Page 0
-** Address 8000h ~ BFFFh: Swappable (Page selected in [[83:Ports:00]]/[[83:Ports:02]])
-** Address C000h ~ FFFFh: RAM Page 1
-* Bits 1 and 2 control the hardware timer frequency. Setting both 0 sets the timer to the fastest speed, and both 1 is the slowest speed. The normal speed is with both bits 1.
 * Bit 3: Unused? Always 0.
 * Bit 4: Timer frequency multiplier; when this bit is set, all the times are multiplied by 90% (i. e. it's 11.1% faster) compared to when it's reset.
@@ Line 27: / Line 18: @@
 == Comments ==
 To calculate the resulting timer frequency you can use the following formula:
 freq = 1800 * ((out_value & 0x10) ? 1.0 : 0.9) / (3 + ((out_value & 0x06) << 1))

← Older revision		Revision as of 08:14, 3 April 2005
Line 31:		Line 31:
	To calculate the resulting timer frequency you can use the following formula:		To calculate the resulting timer frequency you can use the following formula:

−	freq = 1800 * ((out_value & 0x10) ? 1.0 : 0.9) / (3 + ((out_value & 0x06) << 1)) ~~/ 6000000~~	+	freq = 1800 * ((out_value & 0x10) ? 1.0 : 0.9) / (3 + ((out_value & 0x06) << 1))

@@ Line 29: / Line 29: @@
 The calculator uses mode 0 for normal operation. If you change the memory map mode be sure to change it back before returning control.
-To calculate resulting timer frequency you can use the following formula:
+To calculate the resulting timer frequency you can use the following formula:
 freq = 1800 * ((out_value & 0x10) ? 1.0 : 0.9) / (3 + ((out_value & 0x06) << 1)) / 6000000

@@ Line 8: / Line 8: @@
 === Read Values ===
-* Bits 0-7: Undocumented. This port is never read by the TIOS.
+This is a mirror of the link port.
 === Write Values ===