NS16C2552 Datasheet, PDF (19/50 Pages) National Semiconductor (TI) – Dual UART with 16-byte/64-byte FIFOs and up to 5 Mbit/s Data Rate

NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
NOTE
For baud rates of 250k, 300k, 375k, 500k, 750k and 1.5M using a 24MHz crystal causes
minimal error.
ALTERNATE FUNCTION REGISTER (AFR)
This is a read/write register used to select simultaneous write to both register sets and alter MF pin functions.
Bit
Bit Name
Default
7:3
Reserved
2:1
MF Output Sel
0 Concurrent Write
Ena
Table 18. AFR (0x2, LCR[7] = 1, LCR != 0xBF)
R/W
Def
Description
Reserved
These bits are set to a logic 0.
R/W Multi-function Pin Output Select
0
These select the output signal that will be present on the multi-function pin, MF. These bits are
individually programmable for each channel, so that different signals can be selected on each
channel.
AFR[2] AFR[1]
MF Function
1
1
= Reserved (MF output is forced logic 1)
1
0
= RXRDY
0
1
= BAUDOUT
0
0
= OUT2 (default)
R/W Concurrent Write Enable
0
1 = CPU can write concurrently to the same register in both registers sets. This function is
intended to reduce the DUART initialization time. It can be used by a CPU when both channels
are initialized to the same state. The CPU can set or clear this bit by accessing either register set.
When this bit is set the channel select pin still selects the channel to be accessed during read
operations. Setting or clearing this bit has no effect on read operations.
The user should ensure that the DLAB bit LCR[7] of both channels are in the same state before
executing a concurrent write to register addresses 0, 1 and 2.
0 = No concurrent write (default). (No impact on read operations.)
DEVICE IDENTIFICATION REGISTER (ID)
The device ID for NS16C2552 is 0x03. DLL and DLM should be initialized to 0x00 before reading the ID register.
This is a read-only register.
Table 19. DREV (0x0, LCR[7]=1, LCR!=0xBF, DLL=DLM=0x00)
Bit
Bit Name
R/W
Def
Description
7:4
Device ID
R Device ID
Value = 0x3 for NS16C2552; 0x2 for NS16C2752
3:0
Device Rev
R Device Revision
Value = 0x1.
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