SP37E760 Datasheet, PDF (45/78 Pages) SMSC Corporation – 3.3 V I/O CONTROLLER FOR EMBEDDED APPLICATIONS

7 CONFIGURATION
The configuration of the SP37E760 is programmed through hardware selectable Configuration Access Ports that
appear when the chip is placed into the configuration state. The SP37E760 logical device blocks, if enabled, will
operate normally in the configuration state.
7.1 Configuration Access Ports
The Configuration Access Ports are the CONFIG PORT, the INDEX PORT, and the DATA PORT (Table 23). The
base address of these registers is controlled by the nRTS2/SYSOPT pin (see Table 1). To determine the
configuration base address, the state of the nRTS2/SYSOPT pin is latched by the falling edge of a hardware reset. If
the latched state is a 0, the base address of the Configuration Access Ports is located at address 3F0H; if the latched
state is a 1, the base address is located at address 370H.
PORT NAME
CONFIG PORT
INDEX PORT
DATA PORT
Table 23 - Configuration Access Ports
SYSOPT = 0
SYSOPT = 1
0x3F0
0x370
0x3F0
0x370
INDEX PORT + 1
TYPE
WRITE
READ/WRITE^1,2
READ/WRITE¹
Note¹: The INDEX and DATA ports are active only when the SP37E760 is in the configuration state.
Note²: The INDEX PORT is only readable in the configuration state.
7.2 Configuration State
The configuration registers are used to select programmable chip options. The SP37E760 operates in two possible
states: the run state and the configuration state. After power up by default the chip is in the run state. To program
the configuration registers, the configuration state must be explicitly enabled. Programming the configuration
registers typically follows this sequence:
1. Enter the Configuration State,
2. Program the Configuration Register(s),
3. Exit the Configuration State.
7.2.1 ENTERING THE CONFIGURATION STATE
To enter the configuration state write the Configuration Access Key to the CONFIG PORT. The Configuration Access
Key is one byte of 55H data. The SP37E760 will automatically activate the Configuration Access Ports following this
procedure.
7.2.2 CONFIGURATION REGISTER PROGRAMMING
The SP37E760 contains configuration registers CR00-CR2F. After the SP37E760 enters the configuration state,
configuration registers can be programmed by first writing the register index number (00 - 2FH) to the Configuration
Select Register (CSR) through the INDEX PORT and then writing or reading the configuration register contents
through the DATA PORT. Configuration register access remains enabled until the configuration state is explicitly
exited.
7.2.3 EXITING THE CONFIGURATION STATE
To exit the configuration state, write one byte of AAH data to the CONFIG PORT. The SP37E760 will automatically
deactivate the Configuration Access Ports following this procedure, at which point configuration register access
cannot occur until the configuration state is explicitly re-enabled.
SMSC DS – SP37E760
Page 45
Rev. 04/13/2001