83Plus:Ports:10 - Revision history

CVSoft: /* Comments */ Corrected information about new display drivers

2021-09-15T03:36:18Z

‎Comments: Corrected information about new display drivers

Fghsgh: change link to comments

2020-03-12T23:15:45Z

change link to comments

Fghsgh: bit 7 on new revisions: forgot one "not" which completely changes the meaning

2020-03-12T23:13:53Z

bit 7 on new revisions: forgot one "not" which completely changes the meaning

Fghsgh: new LCDs don't read bit 7 correctly

2020-03-08T01:43:23Z

new LCDs don't read bit 7 correctly

Fghsgh: add comments on newer calculators and renew link to datasheet

2020-03-04T00:04:48Z

add comments on newer calculators and renew link to datasheet

Dr. D'nar at 05:09, 22 March 2014

2014-03-22T05:09:01Z

Runer112: Changed the description for [0C-0F] outputs | Fixed every code example

2011-06-11T19:31:37Z

Changed the description for [0C-0F] outputs | Fixed every code example

Andrei.computer: /* Write Values */

2011-03-08T00:34:36Z

‎Write Values

Dwedit at 07:03, 5 October 2008

2008-10-05T07:03:29Z

Dwedit at 16:22, 26 May 2007

2007-05-26T16:22:33Z

@@ Line 61: / Line 61: @@
 But I would advise you actually make use of these waste cycles somehow (process a buffer or something).
-On some newer calculators, a fixed delay can still be used in combination with slowing the CPU through port [[83Plus:Ports:20|20]] and/or adjusting ports [[83Plus:Ports:29|29]] and [[83Plus:Ports:2A|2A]].  However, a large number of calculators have been produced recently whose LCD drivers, for whatever reason, do not respond as quickly.  For this reason, except where the speed loss is absolutely unacceptable (such as for grayscale display) fixed delays should '''not''' be used.  Instead either use the routine at 000B, or poll this port or [[83Plus:Ports:02|Port 02h]] manually.
+On some newer calculators, a fixed delay can still be used in combination with slowing the CPU through port [[83Plus:Ports:20|20]] and/or adjusting ports [[83Plus:Ports:29|29]] and [[83Plus:Ports:2A|2A]].
-Since recently (late 2018), new calculators have started appearing which do not set the 7th bit when busy. Therefore, you can't use it to check if the LCD is ready. The best workaround is to wait for long enough and hope for the best, or use a different port to measure the delay.
+Since recently (late 2018), new calculators have started appearing which may alter the internal video RAM pointer when the status port is read. Therefore, you can't use it to check if the LCD is ready. Routines like ION FastCopy, which use the status port to check if the LCD driver is busy, will cause the displayed image to [https://i.imgur.com/8fWThqo.jpg appear garbled] on these new LCD drivers. These LCD drivers, like the Novateks, are quite fast and don't actually need a busy delay (they can be written to reliably with OTIR at 6 MHz); however, eliminating the busy delay will break backwards compatibility with Toshiba LCD drivers. The workaround is to use a fixed delay of 10 microseconds instead of reading the status port, or use a different port to measure LCD delay.
 ===Unused screen area===
-The LCD driver's video memory holds a display 120 pixels wide, even though the screen is only 96 pixels wide.  The 24 pixel wide offscreen area can still be read from and written to, and is not affected by soft power-off.
+On the T6A04 and T6A04A, the LCD driver's video RAM holds a display 120 pixels wide, even though the screen is only 96 pixels wide. On the T6K04, the video RAM is 128 pixels wide. The extra off-screen area can still be read from and written to, and is not affected by soft power-off. Newer calculators with Novatek display drivers do not have this extra memory.
 ===Test mode===
-This is a very dangerous mode. The first test mode command (1C~1F) causes the screen to receive an unusually high amount of energy. The result is that the screen seems to go blank, save for a single blue(!) line on the TI 83, but on the TI 84's, the entire screen turns blue! Each subsequent command adds more blue lines. After you've had your fill of blueness, exit test mode by sending a exit test mode command (18), which also sets the contrast to it's highest. Now why is it dangerous? Sure it looks cool to make a supposedly black and white LCD to display BLUE, but you are pumping so much energy through the LCD to get this effect that leaving it in this mode for too long can cause long-term damage. Ever left your monitor on for a day or two and forget to set a screen saver? Remember how when you turned it off a burnt image of your screen remained? Well that's what can happen if you leave test mode on for too long. Other possible side effects include "dead pixels" (pixels that stay off no matter what you do).
+This is a very dangerous mode. The first test mode command (1C~1F) causes the screen to receive an unusually high amount of energy. The result is that the screen seems to go blank, save for a single blue(!) line on the TI-83 Plus, but on the TI-84-series calculators, the entire screen turns blue! Each subsequent command adds more blue lines. After you've had your fill of blueness, exit test mode by sending a exit test mode command (18), which also sets the contrast to it's highest. Now why is it dangerous? Sure it looks cool to make a supposedly black and white LCD to display BLUE, but you are pumping so much energy through the LCD to get this effect that leaving it in this mode for too long can cause long-term damage. Ever left your monitor on for a day or two and forget to set a screen saver? Remember how when you turned it off a burnt image of your screen remained? Well that's what can happen if you leave test mode on for too long. Other possible side effects include "dead pixels" (pixels that stay off no matter what you do).
 So don't use test mode okay? Just pretend you didn't hear about it...

@@ Line 24: / Line 24: @@
 * Bit 5: Set if the display is enabled. Reset if disabled. (Note: LCD is completely turned off via [[83Plus:Ports:03|Port 03h]].)
 * Bit 6: Set if the LCD will transfer 8 bits at a time through [[83Plus:Ports:11|Port 11]]. Reset if the LCD will only transfer 6 bits at a time.
-* Bit 7: Set if the LCD is busy. Reset if a command can be accepted. (Not on newer models, see [[#Comments|Comments]].)
+* Bit 7: Set if the LCD is busy. Reset if a command can be accepted. (Not on newer models, see [[#Necessary_LCD_communication_delay|Comments]].)
 === Write Values ===

@@ Line 24: / Line 24: @@
 * Bit 5: Set if the display is enabled. Reset if disabled. (Note: LCD is completely turned off via [[83Plus:Ports:03|Port 03h]].)
 * Bit 6: Set if the LCD will transfer 8 bits at a time through [[83Plus:Ports:11|Port 11]]. Reset if the LCD will only transfer 6 bits at a time.
-* Bit 7: Set if the LCD is busy. Reset if a command can be accepted. (Also see [[#Comments|Comments]].)
+* Bit 7: Set if the LCD is busy. Reset if a command can be accepted. (Not on newer models, see [[#Comments|Comments]].)
 === Write Values ===
@@ Line 63: / Line 63: @@
 On some newer calculators, a fixed delay can still be used in combination with slowing the CPU through port [[83Plus:Ports:20|20]] and/or adjusting ports [[83Plus:Ports:29|29]] and [[83Plus:Ports:2A|2A]].  However, a large number of calculators have been produced recently whose LCD drivers, for whatever reason, do not respond as quickly.  For this reason, except where the speed loss is absolutely unacceptable (such as for grayscale display) fixed delays should '''not''' be used.  Instead either use the routine at 000B, or poll this port or [[83Plus:Ports:02|Port 02h]] manually.
-Since recently (late 2018), new calculators have started appearing which set the 7th bit when busy. Therefore, you can't use it to check if the LCD is ready. The best workaround is to wait for long enough and hope for the best, or use a different port.
+Since recently (late 2018), new calculators have started appearing which do not set the 7th bit when busy. Therefore, you can't use it to check if the LCD is ready. The best workaround is to wait for long enough and hope for the best, or use a different port to measure the delay.
 ===Unused screen area===

@@ Line 23: / Line 23: @@
 * Bit 4: Set if in reset state, reset if in operating state. (Whatever that means.)
 * Bit 5: Set if the display is enabled. Reset if disabled. (Note: LCD is completely turned off via [[83Plus:Ports:03|Port 03h]].)
-* Bit 6: Set if the LCD will transfer 8 bits at a time through [[83Plus:Ports:11|Port 11]]. Reset if the LCD will only trasfer 6 bits at a time.
+* Bit 6: Set if the LCD will transfer 8 bits at a time through [[83Plus:Ports:11|Port 11]]. Reset if the LCD will only transfer 6 bits at a time.
-* Bit 7: Set if the LCD is busy. Reset if a command can be accepted.
+* Bit 7: Set if the LCD is busy. Reset if a command can be accepted. (Also see [[#Comments|Comments]].)
 === Write Values ===
@@ Line 53: / Line 53: @@
 As mentioned, a 10 microsecond delay is required after sending the command. TI provides a routine at 000B (use normal CALL, not BCALL) that will delay the required amount of time. (Because this was not originally an LCD delay routine, on OS's prior to 1.13, calling it destroys the zero flag.)
-On older calculators, this code sequence should also provide sufficient delay while also preserving the zero flag:
+On older calculators, this code sequence should also provide sufficient delay while also preserving the carry flag:
   <nowiki> ex (sp),hl ;19
   ex (sp),hl ;38
@@ Line 61: / Line 61: @@
 But I would advise you actually make use of these waste cycles somehow (process a buffer or something).
-On some newer calculators, a fixed delay can still be used in combination with slowing the CPU through port [[83Plus:Ports:20|20]] and/or adjusting ports [[83Plus:Ports:29|29]] and [[83Plus:Ports:2A|2A]].  However, a large number of calculators have been produced recently whose LCD drivers, for whatever reason, do not respond as quickly.  For this reason, except where the speed loss is absolutely unacceptable (such as for grayscale display) fixed delays should '''not''' be used.  Instead either use the routine at 000B, or poll this port or [[83Plus:Ports:02|port 2]] manually.
+On some newer calculators, a fixed delay can still be used in combination with slowing the CPU through port [[83Plus:Ports:20|20]] and/or adjusting ports [[83Plus:Ports:29|29]] and [[83Plus:Ports:2A|2A]].  However, a large number of calculators have been produced recently whose LCD drivers, for whatever reason, do not respond as quickly.  For this reason, except where the speed loss is absolutely unacceptable (such as for grayscale display) fixed delays should '''not''' be used.  Instead either use the routine at 000B, or poll this port or [[83Plus:Ports:02|Port 02h]] manually.
 ===Unused screen area===

@@ Line 70: / Line 70: @@
 So don't use test mode okay? Just pretend you didn't hear about it...
 == Cursor movement and out-of-bounds behavior ==
@@ Line 102: / Line 107: @@
 == See Also ==
 * [[83Plus:Ports:11|Port 11]] - LCD Data Port
-* [http://wikiti.denglend.net/stuff/t6a04.pdf LCD driver datasheet]
+* [https://archive.org/details/t6a04a-datasheet LCD driver datasheet]

@@ Line 7: / Line 7: @@
 '''Function:''' LCD Command and Status Port
-This port is used to check the status of and send commands to the TI-83+'s LCD Driver.
+This port is used to check the status of and send commands to the calculator's LCD driver.
 '''Note: Official documentation for the LCD controller uses "X" to refer to rows and "Y" to refer to columns.'''

@@ Line 33: / Line 33: @@
 * 07 : Set Y auto-increment mode. Every read or write operation from the data port will cause the LCD's internal pointer to move '''right''' one column.
 * [08~0B]: Set power supply enhancement. You'd be well advised to just leave this alone.
-* [0C~0F]: Performs various screen mirrors, flips, and rotations. 0C enable Normal mode, 0D causes a horizontal mirror, 0E causes a vertical mirror, and 0F turns the screen 180 degrees(A rotation, not a mirroring)
+* [0C~0F]: Applies screen mirroring on newer calculators. Bit 0 set enables horizontal mirroring, bit 1 set enables vertical mirroring.
 * [10~13]: Set power supply level. You'd be well advised to just leave this alone.
 * [14~17]: Undefined.
@@ Line 49: / Line 49: @@
 On older calculators, this code sequence should also provide sufficient delay while also preserving the zero flag:
-  <nowiki>&nbsp;push hl ;15
+  <nowiki> ex (sp),hl ;19
-  push de ;30
+  ex (sp),hl ;38
-  pop de ;44
+  inc (hl)   ;49
-  pop hl ;58
+  dec (hl)   ;60</nowiki>
- nop ;62</nowiki>
 But I would advise you actually make use of these waste cycles somehow (process a buffer or something).
@@ Line 80: / Line 79: @@
 == Example ==
 Turn the LCD "off" and back "on".
-  <nowiki>&nbsp;ld a, 02h
+  <nowiki> ld a,02h
-  out (10h), a
+  out (10h),a
-  push hl ;Or do something else that takes ~60 TStates.
+  ex (sp),hl ;Or do something else that takes ~60 cycles.
-  push de
+  ex (sp),hl
-  pop de
+  inc (hl)
- pop hl
+  dec (hl)
-  nop
   inc a
-  out (10h), a</nowiki>
+  out (10h),a</nowiki>
 Safely wait for the LCD to become available
   <nowiki>lcd_busy_loop:
-  in a,($10) ;we don't care about the value of A, but are interested in the "Negative" flag returned by bit 7
+  in a,($10) ;bit 7 set if LCD is busy
-  jp m,lcd_busy_loop</nowiki>
+  rla

@@ Line 8: / Line 8: @@
 This port is used to check the status of and send commands to the TI-83+'s LCD Driver.
 === Read Values ===
@@ Line 22: / Line 24: @@
 Writing this port sends a command to the LCD. Once you send a command, wait until bit 7 reads 0 before sending another. You need a minimum delay of 10 microseconds (60 cycles of whatever else on the 6MHz TI-83+, or ~150 on a TI-83+ Silver or any TI-84+ when running in [[83Plus:Ports:20|fast mode]]).
-* 00 : Switch to 6-bit mode. ([[83Plus:Ports:11|Port 11]] transfers 6-bits at a time.)
+* 00 : Switch to '''6-bit mode'''. ([[83Plus:Ports:11|Port 11]] transfers 6-bits at a time.)
-* 01 : Switch to 8-bit mode. ([[83Plus:Ports:11|Port 11]] transfers 8-bits at a time.)
+* 01 : Switch to '''8-bit mode'''. ([[83Plus:Ports:11|Port 11]] transfers 8-bits at a time.)
 * 02 : Disable the screen. This blanks the screen and disconnects the LCD RAM from the physical screen, thus allowing you to use the LCD RAM as extra saferam. (But accessing it is so horribly slow that you should only do this if the usual saferam areas aren't enough and you don't need to display anything.)
 * 03 : Enable the screen. This resumes displaying the LCD's RAM contents to the physical screen. (So any garbage you put into LCD RAM while it was off will show up, so B_CALL ClrLCDFull before this!)
-* 04 : Set X auto-decrement mode. Every read or write operation from the data port will cause the LCD's internal pointer to move up one row.
+* 04 : Set X auto-decrement mode. Every read or write operation from the data port will cause the LCD's internal pointer to move '''up''' one row.
-* 05 : Set X auto-increment mode. Every read or write operation from the data port will cause the LCD's internal pointer to move down one row. The TI-83+ expects the LCD to be in this mode for most display routines.
+* 05 : Set X auto-increment mode. Every read or write operation from the data port will cause the LCD's internal pointer to move '''down''' one row. The TI-83+ expects the LCD to be in this mode for most display routines.
-* 06 : Set Y auto-decrement mode. Every read or write operation from the data port will cause the LCD's internal pointer to move left one column.
+* 06 : Set Y auto-decrement mode. Every read or write operation from the data port will cause the LCD's internal pointer to move '''left''' one column.
-* 07 : Set Y auto-increment mode. Every read or write operation from the data port will cause the LCD's internal pointer to move right one column.
+* 07 : Set Y auto-increment mode. Every read or write operation from the data port will cause the LCD's internal pointer to move '''right''' one column.
 * [08~0B]: Set power supply enhancement. You'd be well advised to just leave this alone.
 * [10~13]: Set power supply level. You'd be well advised to just leave this alone.
@@ Line 36: / Line 38: @@
 * [19~1B]: Undefined.
 * [1C~1F]: Enter test mode (see Comments).
-* [20~3F]: Set column.  [20~2E] are valid columns in 8-bit mode, [20~33] are valid columns in 6-bit mode. [34~3F] values are also accepted, but do not correspond to a drawable area.
+* [20~3F]: '''Set column'''.  [20~2E] are valid columns in 8-bit mode, [20~33] are valid columns in 6-bit mode. [34~3F] values are also accepted, but do not correspond to a drawable area.
 * [40~7F]: "Z addressing" (It just changed what phyiscal row the top row of RAM is displayed on. The LCD will wrap the bottom of it's RAM to the top of the screen as needed.)
-* [80~BF]: Set row.
+* [80~BF]: '''Set row'''.
-* [C0~FF]: Set contrast. (C0 is lowest. Note that there is a [[83Plus:RAM:8447|System RAM area (contrast)]] for this which will need to be updated if you want 2nd+Up/2nd+Down to change the contrast as expected (instead of causing a sudden jump...).)
+* [C0~FF]: '''Set contrast'''. (C0 is lowest. Note that there is a [[83Plus:RAM:8447|System RAM area (contrast)]] for this which will need to be updated if you want 2nd+Up/2nd+Down to change the contrast as expected (instead of causing a sudden jump...).)
 == Comments ==
@@ Line 46: / Line 48: @@
 On older calculators, this code sequence should also provide sufficient delay while also preserving the zero flag:
-  <nowiki> push hl ;15
+  <nowiki>&nbsp;push hl ;15
   push de ;30
   pop de ;44
@@ Line 77: / Line 79: @@
 == Example ==
 Turn the LCD "off" and back "on".
-  <nowiki>ld a, 02h
+  <nowiki>&nbsp;ld a, 02h
   out (10h), a
   push hl ;Or do something else that takes ~60 TStates.
@@ Line 86: / Line 88: @@
   inc a
   out (10h), a</nowiki>
 == See Also ==
 * [[83Plus:Ports:11|Port 11]] - LCD Data Port
 * [http://wikiti.denglend.net/stuff/t6a04.pdf LCD driver datasheet]

@@ Line 1: / Line 1: @@
 [[Category:83Plus:Ports:By Address|10 - LCD Command/Status Port]][[Category:83Plus:Ports:By Name|LCD Command/Status Port]]
 == Synopsis ==
 '''Port Number:''' 10h