MAX3140 Maxim, MAX3140 Datasheet - Page 17

• Manufacturer Part Number: MAX3140
• Description: SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers
• Manufacturer: Maxim

Table 1. Bit Descriptions
SPI/MICROWIRE-Compatible UART with Integrated
D0t–D7t
D0r–D7r
NAME
B0–B3
B0–B3
RAM
RAM
CTS
FEN
FEN
RTS
BIT
PM
PM
RM
RM
PE
PE
IR
IR
Pt
Pr
L
L
R
TYPE
write
write
write
write
write
write
write
write
write
write
write
read
read
read
read
read
read
read
read
read
read
read
read
BIT
______________________________________________________________________________________
True Fail-Safe RS-485/RS-422 Transceivers
XXXXXXXX
00000000
change
STATE
POR
0000
0000
No
X
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Baud-Rate Divisor Select Bits. Sets the baud clock’s value (Table 6).
Baud-Rate Divisor Select Bits. Reads the 4-bit baud clock value assigned to these registers.
Clear-to-Send-Input. Records the state of the CTS pin (CTS bit = 0 implies CTS pin = logic
high).
Transmit-Buffer Register. Eight data bits written into the transmit-buffer register. D7t is ignored
when L = 1.
Eight data bits read from the receive FIFO or the receive-buffer register. When L = 1, D7r is
always 0.
FIFO Enable. Enables the receive FIFO when FEN = 0. When FEN = 1, FIFO is disabled.
FIFO-Enable Readback. FEN’s state is read.
Enables the IrDA timing mode when IR = 1.
Reads the value of the IR bit.
Bit to set the word length of the transmitted or received data. L = 0 results in 8-bit words
(9-bit words if PE = 1) (see Figure 5). L = 1 results in 7-bit words (8-bit words if PE = 1).
Reads the value of the L bit.
Transmit-Parity Bit. This bit is treated as an extra bit that is transmitted if PE = 1. In 9-bit net-
works, the MAX3140 does not calculate parity. If PE = 0, then this bit (Pt) is ignored in transmit
mode (see the 9-Bit Networks section).
Receive-Parity Bit. This bit is the extra bit received if PE = 1. Therefore, PE = 1 results in 9-bit
transmissions (L = 0). If PE = 0, then Pr is set to 0. Pr is stored in the FIFO with the receive
data (see the 9-Bit Networks section).
Parity-Enable Bit. Appends the Pt bit to the transmitted data when PE = 1, and sends the Pt
bit as written. No parity bit is transmitted when PE = 0. With PE = 1, an extra bit is expected to
be received. This data is put into the Pr register. Pr = 0 when PE = 0. The MAX3140 does not
calculate parity.
Reads the value of the Parity-Enable bit.
Mask for Pr bit. IRQ is asserted if PM = 1 and Pr = 1 (Table 7).
Reads the value of the PM bit (Table 7).
Receive Bit or FIFO Not Empty Flag. R = 1 means new data is available to be read or is being
read from the receive register or FIFO. If performing a READ DATA or WRITE DATA operation,
the R bit will clear on the falling edge of SCLK's 16th pulse if no new data is available.
Mask for R bit. IRQ is asserted if RM = 1 and R = 1 (Table 7).
Reads the value of the RM bit (Table 7).
Mask for RA/FE bit. IRQ is asserted if RAM = 1 and RA/FE = 1 (Table 7).
Reads the value of the RAM bit (Table 7).
Request-to-Send Bit. Controls the state of the RTS output. This bit is reset on power-up (RTS
bit = 0 sets the RTS pin = logic high).
DESCRIPTION
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