CS7654 datasheet(28/62 Pages) CIRRUS

28 / 62 page

CS7654

EPROM are aborted and the NODEV status bit is

set in status register at address 01h at SA 0x34h.

The data within the EPROM is formatted in three-

byte packets that represent the destination address,

the CS7654 initiates an I2C bus cycle using the first

byte as the device station address, the second byte

as the device register address, and the third byte as

the data being written to the device. If an acknowl-

edge is received from the target device, the CS7654

will fetch the next 3 bytes from the EPROM and re-

peat the process. The only exception being the

gamma table whose entire 256 bytes is transferred

in one I2C write cycle. This process will continue

until the total number of packets read equals the

value in the EEPROM count register (registers 1Ah

and 1Bh at SA 0x34h), a HALT command is exe-

cuted, or NO ACKNOWLEDGE is received from

the target device.

While the CS7654 is downloading from the

EPROM, the INITACT bit (register 01h bit3 at SA

0x34h) is set in the status register of CS7654. All

attempts to write to CS7654 registers by an external

controller will be ignored during this time.

Controlling the Configuration Process

The simplest configuration would consist of an

EPROM with one configuration file. In this case,

the first commands in the EPROM should write the

total number of packets in the EEPROM. This data

is written to the EEPROM count high and low byte

registers (registers 1Ah and 1Bh at SA 0x34h).

Subsequent bytes would contain all the necessary

data to configure the camera. This data will be read

in a sequential fashion.

If, however, multiple configurations are desired,

the EEPROM may be programmed with multiple

sets of data, and the CS7654 programmed to select

one of 8 configurations. The appropriate configura-

tion is defined by the 3 GPIO[2:0] pins. The

CS7654 incorporates 3 commands to handle multi-

ple configurations: SKIP, JUMP, and HALT.

The SKIP command tells the CS7654 to skip to the

address within the EEPROM specified by the Con-

figuration Control registers (30h - 3Fh

at SA

0x34h). The Configuration Control registers are

used in pairs to provide a 11-bit EEPROM address.

The Configuration Index Register determines

which two of the 8 pairs will be used.

The Configuration Index Register is loaded auto-

matically after reset by the CS7654. The CS7654

will read from the GPIO port. If the read cycle is

successful, the Configuration Index Register will

contain the state of the lower 3 bits of the parallel

I/O port. A set of shunts or DIP switches attached

to the I/O port provides a convenient way to select

up to 8 configurations. The SKIP command is exe-

cuted by writing a 1 to bit 1 of the EEPROM Con-

trol Register (42h at SA 0x34h).

The JUMP is similar to the SKIP command. The

user loads a jump address into the Jump Control

Registers (40h and 41h at SA 0x34h) and then ex-

ecutes the JUMP command by setting bit 2 of the

EEPROM Control Register (42h at SA 0x34h) to a

1. The jump command may be used to reduce the

amount of required EEPROM space by allowing

multiple configurations to share common data. For

example, three configurations may be necessary to

adjust for three different CCD timings, but they

may all share a common gamma table.

The HALT command is used to stop the execution

of the boot state machine. When all necessary data

has been read from the EEPROM, writing a 1 to bit

0 (HALT) of the EEPROM Control Register will

safely stop the boot process.

The total number of packets that may be stored in

the external EEPROM is 2k/3 or 682 3-byte com-

mands. Gamma table packets contain 259bytes.

A typical map of the EPROM table is shown in Fig-

ure 17. The only exception to this organization is

data for the CS7654 gamma table. The data for the

gamma table is organized as shown in Figure 18.

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