Texas Instruments TRF7970A Instruction Manual page 66

TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Table 6-41. Supply-Regulator Setting – Automatic 5-V System
Option Bits Setting in Control Register
Register
B7 B6
00
0B 1
(1) x = don't care
Table 6-42. Supply-Regulator Setting – Automatic 3-V System
Option Bits Setting in Control Register
Register
B7 B6
00
0B 1
(1) x = don't care
6.14.3.3 Status Registers
6.14.3.3.1 IRQ Status Register (0x0C)
Function: Information available about TRF7970A IRQ and TX/RX status
Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read
phase. The reset also removes the IRQ flag.
Bit Name
B7 Irq_tx IRQ set due to end of TX
B6 Irg_srx IRQ set due to RX start
B5 Irq_fifo Signals the FIFO level
B4 Irq_err1 CRC error
B3 Irq_err2 Parity error
B2 Irq_err3 Byte framing or EOF error
B1 Irq_col Collision error
B0 Irq_noresp No-response time interrupt
To reset (clear) the register 0x0C and the IRQ line, the register must be read. During Transmit the
decoder is disabled, only bits B5 and B7 can be changed. During Receive only bit B6 can be changed, but
does not trigger the IRQ line immediately. The IRQ signal is set at the end of Transmit and Receive
phase.
66 Detailed Description
B5 B4 B3 B2
(1)
x
B5 B4 B3 B2
(1)
x
Table 6-43. IRQ Status Register (0x0C)
Function
Signals that TX is in progress. The flag is set at the start of TX but the interrupt
request (IRQ = 1) is sent when TX is finished.
Signals that RX SOF was received and RX is in progress. The flag is set at the
start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.
Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)
register
Indicates receive CRC error only if B7 (no RX CRC) of ISO Control register is
set to 0.
Indicates parity error for ISO14443A
Indicates framing error
Collision error for ISO14443A and ISO15693 single subcarrier. Bit is set if more
then 6 or 7 (as defined in register 0x01) are detected inside one bit period of
ISO14443A 106 kbps. Collision error bit can also be triggered by external
noise.
No response within the "No-response time" defined in RX No-response Wait
Time register (0x07). Signals the MCU that next slot command can be sent.
Only for ISO15693.
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B1 B0
1 5-V system
0 0 Automatic regulator setting 400-mV difference
B1 B0
0 3-V system
0 0 Automatic regulator setting 400-mV difference
Description
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TRF7970A
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