In the course of my efforts of documenting and emulating the Sitronix ST7789 LCD controller in the CE family calculators, I noticed that the internal clock rate (nominally 10 MHz) wasn't totally consistent between my different calculators.

This variance in clock rate is important to know when tuning timing parameters for VSYNC interface mode, because if a VSYNC signal (from the Primecell PL111 LCD controller) comes in before the Sitronix LCD controller is done scanning a frame, that signal is dropped and the refresh rate is halved. I noticed this discrepancy when developing TI-Boy CE against my multiple calculators. Ideally the timing parameters should target a frequency lower than the frequency of any known calculator's LCD controller.

Long story short, I've just developed a test program that allows visually tuning the refresh rate to as close to 60 Hz as possible, and prints the approximate clock rate based on the configured timings on exit. I'd like to collect information on as many calculators as possible to determine the range of clock rates expected in the wild. So far, signs point to this not being related to the revision, but I recommend sharing that for statistical purposes.

I'll start by sharing mine (model and datecode/revision):

TI-84+CE (L-0115): 10,010,880 Hz
TI-84+CE (L-0716C): 10,051,080 Hz
TI-83PCE Python (L-0419M): 9,887,640 Hz

My current idea of a "target clock rate" for VSYNC interface timing parameters is 9.8 MHz, but if anyone finds a clock rate slower than that, it may need to change.
Edit: All (assembled) calcs tested!

84+CE      (L-0315):  10,045,080
84+CE      (L-0317E): 10,061,400
84+CE      (L-0519M): 10,096,200
84+CE Red Sample (M):  9,991,200
84+CE-T Py (L-0520P):  9,891,860
84+CE      (L-0122W): 10,277,520
Here are some of mine:

  • 84+CE Py E1640234D (rev AA): 9,952,440
  • 84+CE Teal sample (revision M): 9,917,280
  • 84+CE K-EVT1-009 (~1017): 9,952,440
  • 84+CE K-EVT1-012 (~0519): 10,102,200
  • 84+CE K-ELG2-EVT3-253 (~0818): 10,066,440
  • 83PCE L-DVT-000270 (~0916): 10,130,880
84+CE (L-0416C) : 10,054,800 Hz
TI-84 Plus CE, L-0617C: 10,054,800 Hz (battery indicator shows full, if that matters)
TI-84 Plus CE, L-0819N: 9,988,440 Hz (battery indicator shows lowest green level)

This seems like the sort of thing that might be affected by battery level, so I am going to charge my rev. N & see if it makes a difference.

EDIT: Apparently the battery level does not affect much after all:
TI-84 Plus CE, L-0819N: 9,987,600 Hz (immediately after charging)

83PCE    L-0215A:   10,121,760
84PCE    L-0215 :   10,084,320
84PCEPy  L-0421S:   10,079,400
83PCE    L-0816E:   10,056,360
84PCET   L-0515A:   10,036,800
83PCE    L-0615B:   (dead batt)
83PCE    L-1016F:   (dead batt)
83PCE    L-0216B1:  10,010,880
84PCE    L-....M:   10,004,040
83PCEEP  L-0419M:    9,999,720
83PCEEP  L-0521S:    9,982,440
83PCE    L-0417I:    9,971,520
83PCE    L-0818L:    9,958,080
84PCEPy  L-0421S:    9,907,800
84+CE-T (L-0419L): 9,977,040
(tested with both high/low battery, charging vs not charging, no difference)
TI-84+CE (L-0215): 10,004,040
TI-84+CE (L-0719M): 10,160,640
TI-83PCE Python (L-0621S): 9,849,000
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