Freescale Semiconductor Application Note Document Number: AN3581 Rev. 0, 02/2008 How to Synchronize Multiple TPM Modules in HCS08 by: HaiNing Liu Asia & Pacific Operation Microcontroller Solutions Group 1 Introduction Many HCS08 microcontrollers offer multiple timer/pulse-width modulators (TPMs). Timer functions are typically used in ways that require them to be related to a single counter. This document explains how to synchronize these TPMs so that all channels operate as if they are related to a single counter. © Freescale Semiconductor, Inc., 2008. All rights reserved. Contents 1 2 3 4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TPM Module on HCS08. . . . . . . . . . . . . . . . . . . . . . . . . . Synchronizing Multiple TPM Modules . . . . . . . . . . . . . . . 3.1 Synchronized using Software . . . . . . . . . . . . . . . . . 3.2 Counter Modes Study . . . . . . . . . . . . . . . . . . . . . . . Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 3 3 3 7 TPM Module on HCS08 2 TPM Module on HCS08 The TPM is very effective for general use and is common to all HCS08 products. Figure 1 shows the structure of a TPM for the HCS08 family. BUS CLOCK FIXED SYSTEM CLOCK SYNC EXTERNAL CLOCK CLOCK SOURCE SELECT OFF, BUS, FIXED SYSTEM CLOCK, EXT PRESCALE AND SELECT ³1, 2, 4, 8, 16, 32, 64, or ³128 CLKSB:CLKSA PS2:PS1:PS0 CPWMS 16-BIT COUNTER TOF COUNTER RESET TOIE INTERRUPT LOGIC 16-BIT COMPARATOR TPMxMODH:TPMxMODL CHANNEL 0 ELS0B ELS0A PORT LOGIC TPMxCH0 16-BIT COMPARATOR TPMxC0VH:TPMxC0VL CH0F 16-BIT LATCH MS0B MS0A CH0IE INTERRUPT LOGIC Figure 1. TPM Architecture The key component of the TPM module is a free running main 16-bit counter with an up/down counting option. The TPM can use a 16-bit module register (TPMxMPDH: TPMxMODL) to control counter range and generate a terminal count interrupt if the main counter matches the value of the modulus register. The TPM includes several stand-alone channels. Each channel can be configured as input-capture mode, output-compare mode, buffered-edge-aligned PWM mode, or center-aligned PWM mode. The channels have the following flexibility: • The input capture trigger can be rising-edge, falling-edge, or any-edge. • The output compare function has set, clear, and toggle options. • PWM outputs have selectable polarity. • All channels can be configured to work at the same center-aligned PWM (CPWM) mode when CPWMS bit in the TPMxSC register is set. • Interrupt request can be enabled or disabled for each channel. How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 2 Freescale Semiconductor Synchronizing Multiple TPM Modules 3 Synchronizing Multiple TPM Modules The multiple TPMs on HCS08s provide the flexibility of multiple time bases, but many applications need channels associated with a common time base. For example, we may combine two TPMs in MC9S08SH8 that will perform exactly like a single 4-channel TPM, so that count transitions occur at exactly the same time in both TPMs. 3.1 Synchronized Using Software The TPM has no external synchronizing/enable pins, but it can be enabled by setting either the CLKSB bit or the CLKSA bit of TPMxSC, or both of these bits, to 1. It can be disabled by clearing these two bits. Here we introduce a software synchronization method with the following assumptions. In other applications, all of these assumptions must be included, but there may be others also. • The clock sources are fixed to the bus clock, so we can enable TPM by setting the CLKSB : CLKSA bit as 0 : 1. • The prescale factor and modulus value of the combined TPMs must be the same. • The count operation modes must be the same, either 16-bit free running (CPWMS = 0) or else up/down (CPWMS = 1). • To prevent interrupt in initializing, all interrupt sources must be disabled. 3.2 Counter Modes Study Because there are two different counter modes — free running and up/down counting — the synchronization implementation will be a little different for each one. 3.2.1 Free-Running Counter (CPWMS = 0) As an up-counter, the main 16-bit counter counts from 0x0000 through its terminal count, and then starts over at 0x0000. The terminal count will be updated by 0xFFFF or a modulus value in TPMxMODH:TPMxMODL. How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 Freescale Semiconductor 3 Synchronizing Multiple TPM Modules Pf * (Mc1 + 1) AB TPM1_modulus E Pf * (Mc + 1) N Pf * (Mc2 + 1) Timing (Bus_cycles) TPM2_modulus CD E Figure 2. Synchronization Mechanism of Combined TPMs on Free-Running Counter The synchronization process is listed below: 1. As shown in Figure 2, enable the TPM1 by initializing the TPM1SC register at time A. The modulus counter starts to run at time B, several bus cycles after time A, because of the instruction execution delay. 2. Enable the TPM2 at time C, and the modulus counter of TPM2 will actually start to run at time D. If using the same assembly code, the instruction execute delay will be the same as for TPM1. 3. To compensate for the delay between TPM1SC write (time A) and TPM2SC write (time C), we introduce Equation 1 to choose the modulus values of TPM1 and TPM2. Mc2 = Mc1 – N / Pf Eqn. 1 Here — Mc2: the modulus value of TPM2 — Mc1: the modulus value of TPM1 — N: the bus cycle delay between TPM1SC write and TPM2SC write — Pf: the desired prescale factor of TPM1 and TPM2. 4. Re-initialize the modulus value of TPM1 and TPM2 to the desired modulo setting (here named Mc) before the first overflow time (time E). These two TPMs will be synchronized at this same Mc after time E. Try to choose smaller values for Mc1 and Mc2, which will have the advantage of making synchronization time shorter (from time A to time E), but make sure to finish initializing these two modulus values during this time interval (from time D to time E). Table 1 lists how to choose these parameters based on Pf. All these parameters have been verified with the attached example project. Example 1 shows the code with Pf = 16. How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 4 Freescale Semiconductor Synchronizing Multiple TPM Modules Table 1. Choose Mc1, Mc2, and N According to Different Values for Pf Pf Mc1 Mc2 N (Bus Cycles) 1 > 21 Mc1 – 4 4 2 > 11 Mc1 – 2 4 4 >5 Mc1 – 1 4 8 >3 Mc1 – 1 8 16 >2 Mc1 – 1 16 32 >1 Mc1 – 1 32 64 >1 Mc1 – 1 64 128 >1 Mc1 – 1 128 Example 1. Code for Pf = 16 asm{ MOV #$00, TPM1MODH MOV #$15, TPM1MODL MOV #$00, TPM2MODH MOV #$11, TPM2MODL LDA #$02; MOV #$0c, TPM1SC Delay1_1: NOP DBNZA Delay1_1 NOP; NOP; MOV #$0c, TPM2SC MOV #$03, TPM1MODH MOV #$e8, TPM1MODL MOV #$03, TPM2MODH MOV #$e8, TPM2MODL //initial Mc1 //initial Mc2 //Pf = 16 //Pf = 16 // update to desired Mc // update to desired Mc } 3.2.2 Up-Down Counter (CPWMS = 1) When CPWMS = 1, the counter counts upward from 0x0000 through its terminal count, then counts downward to 0x0000, where it returns to up-counting. The synchronization mechanism is similar to that described in Section 3.2.1, “Free-Running Counter (CPWMS = 0).” The only difference is to choose different values for Mc1 and Mc2 according to Equation 2. Mc2 = Mc1 - N/ 2 / Pf Eqn. 2 How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 Freescale Semiconductor 5 Synchronizing Multiple TPM Modules 2 * Pf * Mc1 E A B TPM1_modulus 2 * Pf * Mc N 2 * Pf * Mc2 Timing (Bus_cycles) TPM2_modulus CD E Figure 3. Synchronization Mechanism of Combined TPMs in CPWM Mode Table 2 lists how to choose these parameters according to Pf. All the data have been verified by using the attached example. Table 2. Choose Mc1, Mc2, and N According to Different Values for Pf Pf Mc1 Mc2 N (Bus Cycles) 1 > 18 Mc1 – 2 4 2 >9 Mc1 – 1 4 4 >5 Mc1 – 1 8 8 >3 Mc1 – 1 16 16 >2 Mc1 – 1 32 32 >2 Mc1 – 1 64 64 >2 Mc1 – 1 128 128 >2 Mc1 – 1 256 How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 6 Freescale Semiconductor Conclusion 4 Conclusion We introduce a software method to synchronize two TPMs on HCS08s and let them relate to a single timebase. An example project is provided for reference. This project is based on the MC9S08SH8 demo board and CodeWarrior for HC(S)08 V5.1 with the SH8 service pack. How to Synchronize Multiple TPM Modules in HCS08, Rev. 0 Freescale Semiconductor 7 How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support Europe, Middle East, and Africa: Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) www.freescale.com/support Japan: Freescale Semiconductor Japan Ltd. Headquarters ARCO Tower 15F 1-8-1, Shimo-Meguro, Meguro-ku, Tokyo 153-0064 Japan 0120 191014 or +81 3 5437 9125 [email protected] Asia/Pacific: Freescale Semiconductor Hong Kong Ltd. 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