ZHCS363L August 2011 – March 2017 TRF7970A
PRODUCTION DATA.
The frequency of SYS_CLK (pin 27) is programmable by the bits B4 and B5 of this register. The frequency of the TRF7970A system clock oscillator is divided by 1, 2 or 4 resulting in available SYS_CLK frequencies of 13.56 MHz or 6.78 MHz or 3.39 MHz.
The ASK modulation depth is controlled by bits B0, B1 and B2. The range of ASK modulation is 7% to 30% or 100% (OOK). The selection between ASK and OOK (100%) modulation can also be done using direct input OOK (pin 12). The direct control of OOK/ASK using OOK pin is only possible if the function is enabled by setting B6 = 1 (en_ook_p) in this register (0x09) and the ISO Control Register (0x01, B6 = 1). When configured this way, the MOD (pin 14) is used as input for the modulation signal.
Table 6-36 describes the Modulator and SYS_CLK Control register.
Function: Controls the modulation input and depth, ASK / OOK control and clock output to external system (MCU) | ||||||
Default: 0x91 at POR = H or EN = L, and at each write to ISO control register, except Clo1 and Clo0. | ||||||
Bit | Name | Function | Description | |||
B7 | 27MHz | Enables 27.12-MHz crystal | Default = 1 (enabled) | |||
B6 | en_ook_p | 1 = Enables external selection of ASK or OOK modulation 0 = Default operation as defined in B0 to B2 (0x09) |
Enable ASK/OOK pin (pin 12) for "on the fly change" between any preselected ASK modulation as defined by B0 to B2 and OOK modulation: If B6 is 1, pin 12 is configured as follows: 1 = OOK modulation 0 = Modulation as defined in B0 to B2 (0x09) |
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B5 | Clo1 | SYS_CLK output frequency MSB | Clo1 | Clo0 | SYS_CLK Output (if 13.56-MHz crystal is used) | SYS_CLK Output (if 27.12-MHz crystal is used) |
0 | 0 | Disabled | Disabled | |||
0 | 1 | 3.39 MHz | 6.78 MHz | |||
B4 | Clo0 | SYS_CLK output frequency LSB | 1 | 0 | 6.78 MHz | 13.56 MHz |
1 | 1 | 13.56 MHz | 27.12 MHz | |||
B3 | en_ana | 1 = Sets pin 12 (ASK/OOK) as an analog output 0 = Default |
For test and measurement purpose. ASK/OOK pin 12 can be used to monitor the analog subcarrier signal before the digitizing with DC level equal to AGND. | |||
B2 | Pm2 | Modulation depth MSB | Pm2 | Pm1 | Pm0 | Mod Type and % |
0 | 0 | 0 | ASK 10% | |||
0 | 0 | 1 | OOK (100%) | |||
B1 | Pm1 | Modulation depth | 0 | 1 | 0 | ASK 7% |
0 | 1 | 1 | ASK 8.5% | |||
1 | 0 | 0 | ASK 13% | |||
B0 | Pm0 | Modulation depth LSB | 1 | 0 | 1 | ASK 16% |
1 | 1 | 0 | ASK 22% | |||
1 | 1 | 1 | ASK 30% |