CLRC632 Datasheet, PDF (118/163 Pages) NXP Semiconductors – Multiple Protocol Contactless Reader IC

Philips Semiconductors
Product Specification Rev. 3.0; May 2003
Multiple Protocol Contactless Reader IC
CL RC632
If TxLastBits is unequal zero the last byte is not transmitted completely, but only the number of bits set in
TxLastBits are transmitted (starting with the least significant bit).
Thus, the internal state machine has to check the FIFO status at an earlier point in time (shown in the figure
below).
N_WR (FIFO Data)
TxLastBits
TxLastBits = 4
FIFO Length
0x01
0x00
0x01
FIFO empty
TxData Bit4
Bit7 Bit0
Bit3 Bit4
Bit7 Bit0
Check FIFO empty
Accept Further Data
0x00
Bit3
Figure 18-3: Timing for Transmitting Bit Oriented Frames
Since TxLastBits = 4 in this example, transmission stops after Bit 3 is transmitted. If configured, the frame is
completed with an EOF.
The figure above also shows a write access to the FIFOData Register right before the FIFO’s status is
checked. This leads to ‘FIFO empty’ going to 0 again and therefore ‘Accept Further Data’ stays active. The
new byte written is transmitted via the RF-interface.
‘Accept Further Data’ is changed only by the ‘Check FIFO empty’ function. This function verifies ‘FIFO empty’
one bit duration before the last expected bit transmission.
Frame Definition
8 Bit with Parity
8 Bit without Parity
x Bit without Parity
Verification at:
8^th Bit
7^th Bit
(x-1)^th Bit
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