83Plus:Ports:20 - Revision history

NonstickAtom: Added another cpu speed switch documented by the_mad_joob

2020-12-09T18:32:01Z

Added another cpu speed switch documented by the_mad_joob

Fghsgh: add details about TA1

2020-07-02T21:49:26Z

add details about TA1

Fghsgh: add TA1 information

2020-03-04T00:55:19Z

add TA1 information

Fghsgh: /* Comments */

2020-03-04T00:14:38Z

‎Comments

Dr. D'nar: Added some extra information on the CPU speed values

2014-03-28T04:22:51Z

Added some extra information on the CPU speed values

Michael: /* Comments */

2006-05-07T05:44:20Z

‎Comments

Jim e: Spell check (god i'm dyslexic)

2005-08-23T14:11:44Z

Spell check (god i'm dyslexic)

Jim e: More info on modes

2005-08-21T20:26:04Z

More info on modes

Michael: /* Read Values */

2005-04-05T02:27:00Z

‎Read Values

FloppusMaximus at 20:59, 30 March 2005

2005-03-30T20:59:53Z

@@ Line 57: / Line 57: @@
   out (20h), a</nowiki>
-The only side effect of this is that on the TI-83+ Basic this will cause both linkport lines to go high - which shouldn't matter too much if you're not using the linkport at that time, especially since both lines are high normally...
+The only side effect of this is that on the TI-83+ Basic this will cause both linkport lines to go high - which shouldn't matter too much if you're not using the linkport at that time, especially since both lines are high normally... the_mad_joob discovered that this method will switch to CPU speed 3, not 1.
 == Credits and Contributions ==
 * '''Michael Vincent:''' Documentation and his faster approach as found [http://michaelv.org/programs/calcs/ports/port20.html here].

@@ Line 41: / Line 41: @@
 Newer models (with new TA1 ASICs with fewer pins) don't show any difference between 01~03, suggesting that the extra pins for speeds 02 and 03 don't exist. Furthermore, the speed is closer to 16 MHz than it is to 15 MHz, even slightly above it on 4 out of 5 calculators I've tested.
-You can actually re-enable the extra values on production models if you find the right pins. On the TI-83+SE, there are helpful solder pads on the PCB; on the TI-84+/C/SE, you have to solder directly to the ASIC. You'll need to find a set of six pins, where one is a ground shared by a capacitor and two resistors, the next is connected to a capacitor, the next is connected to a resistor, the next two are not connected (solder to these pins), and the last is connected to another resistor. On the TA3 ASIC, they're pins 66-72, with 70 and 71 being the pins you want to tap (there are 144 pins, the side with #1 will be marked in some special way, and they're numbered counter-clockwise). On the TA1 ASIC, there are no known pins for this. Experiments on the TI-83+SE showed that the ASIC was unstable above about 22-23 MHz.
+You can actually re-enable the extra values on production models with the TA3 ASIC if you find the right pins. On the TI-83+SE, there are helpful solder pads on the PCB; on the TI-84+/C/SE, you have to solder directly to the ASIC. You'll need to find a set of six pins, where one is a ground shared by a capacitor and two resistors, the next is connected to a capacitor, the next is connected to a resistor, the next two are not connected (solder to these pins), and the last is connected to another resistor. On the TA3 ASIC, they're pins 66-72, with 70 and 71 being the pins you want to tap (there are 144 pins, the side with #1 will be marked in some special way, and they're numbered counter-clockwise). On the TA1 ASIC, there are no known pins for this. Experiments on the TI-83+SE showed that the ASIC was unstable above about 22-23 MHz. The flash chip is only rated for 20 MHz, which could explain the instability.
 == Example ==

@@ Line 41: / Line 41: @@
 Newer models (with new TA1 ASICs with fewer pins) don't show any difference between 01~03, suggesting that the extra pins for speeds 02 and 03 don't exist. Furthermore, the speed is closer to 16 MHz than it is to 15 MHz, even slightly above it on 4 out of 5 calculators I've tested.
-You can actually re-enable the extra values on production models if you find the right pins. On the TI-83+SE, there are helpful solder pads on the PCB; on the TI-84+/C/SE, you have to solder directly to the ASIC. You'll need to find a set of six pins, where one is a ground shared by a capacitor and two resistors, the next is connected to a capacitor, the next is connected to a resistor, the next two are not connected (solder to these pins), and the last is connected to another resistor. On the TA3 ASIC, they're pins 66-72, with 70 and 71 being the pins you want to tap (there are 144 pins, the side with #1 will be marked in some special way, and they're numbered counter-clockwise). Experiments on the TI-83+SE showed that the ASIC was unstable above about 22-23 MHz.
+You can actually re-enable the extra values on production models if you find the right pins. On the TI-83+SE, there are helpful solder pads on the PCB; on the TI-84+/C/SE, you have to solder directly to the ASIC. You'll need to find a set of six pins, where one is a ground shared by a capacitor and two resistors, the next is connected to a capacitor, the next is connected to a resistor, the next two are not connected (solder to these pins), and the last is connected to another resistor. On the TA3 ASIC, they're pins 66-72, with 70 and 71 being the pins you want to tap (there are 144 pins, the side with #1 will be marked in some special way, and they're numbered counter-clockwise). On the TA1 ASIC, there are no known pins for this. Experiments on the TI-83+SE showed that the ASIC was unstable above about 22-23 MHz.
 == Example ==

@@ Line 38: / Line 38: @@
 |}
 I suggest still using 1 as the speed setting value since the speed of the other values may change in the future---unlikely as that may be---, which could seriously mess up your screen routines, or even cause opcode fetches to fail if required delay states are not configured. The slightly extra speed observed is due to capacitance of the unused pins. These modes are distinguished by LCD delaying hardware, ports 29-2C.
 You can actually re-enable the extra values on production models if you find the right pins. On the TI-83+SE, there are helpful solder pads on the PCB; on the TI-84+/C/SE, you have to solder directly to the ASIC. You'll need to find a set of six pins, where one is a ground shared by a capacitor and two resistors, the next is connected to a capacitor, the next is connected to a resistor, the next two are not connected (solder to these pins), and the last is connected to another resistor. On the TA3 ASIC, they're pins 66-72, with 70 and 71 being the pins you want to tap (there are 144 pins, the side with #1 will be marked in some special way, and they're numbered counter-clockwise). Experiments on the TI-83+SE showed that the ASIC was unstable above about 22-23 MHz.

@@ Line 14: / Line 14: @@
 === Write Values ===
-* 00h : Set the CPU to 6MHz.
+* 00h : Set the CPU speed to 6MHz.
-* 01h: Set the CPU to 15MHz.
+* 01h: Set the CPU speed to 15MHz.
 == Comments ==
 This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of [[83Plus:Ports:00|Port 00h]].
-This port can contain values of 2 and 3, but the difference in speed is negligible. Values 2 and 3 were intended for use with 20 MHz and 25 MHz speeds, but this functionality was left out before production began. Using the crystal timers I came to these approximate values.
+This port can contain values of 2 and 3, but the difference in speed is negligible. Michal_V has indicated that values 2 and 3 were intended for use with 20 MHz and 25 MHz speeds, but this functionality was left out before production began. Using the crystal timers I came to these approximate values.
 {| width="30%" border="1" cellspacing="1" bgcolor="white"
 | width="40%" | Port Contents
@@ Line 37: / Line 37: @@
 | width="60%" | ~14.990 mhz
 |}
-I suggest still using 1 as the speed setting value since the total effect of the other values are not known. These modes are distinguished by LCD delaying hardware, ports 29-2C.
+I suggest still using 1 as the speed setting value since the speed of the other values may change in the future---unlikely as that may be---, which could seriously mess up your screen routines, or even cause opcode fetches to fail if required delay states are not configured. The slightly extra speed observed is due to capacitance of the unused pins. These modes are distinguished by LCD delaying hardware, ports 29-2C.
 == Example ==

@@ Line 11: / Line 11: @@
 === Read Values ===
 * 00h : The CPU is running at 6MHz.
-* 01h: THe CPU is running at 15MHz.
+* 01h: The CPU is running at 15MHz.
 === Write Values ===

← Older revision		Revision as of 20:59, 30 March 2005
Line 1:		Line 1:
−	[[Category:83Plus:Ports:By Address\|20 - CPU Speed Port]] [[Category:83Plus:Ports:By Name\|CPU Speed Port]] {{SE-Only Port\|00}}	+	[[Category:83Plus:Ports:By Address\|20 - CPU Speed Port]] [[Category:83Plus:Ports:By Name\|CPU Speed Port]]
		+	{{SE-Only Port\|00}}

	== Synopsis ==		== Synopsis ==