CS8413 datasheet(17/38 Pages) ETC

17 / 38 page

CS8413 CS8414

DS240F1

FLAG1 in status register 1, SR1, can be used to

monitor the channel status buffer. In mode 0,

FLAG1 is set low after channel status byte 23 (the

last byte) is written, and is set high when channel

status byte 15, location 17H is written. If the corre-

sponding interrupt enable bit in IER1 is set, a tran-

sition of FLAG1 will generate a pulse on the

interrupt pin. Figure 12 illustrates the memory

write sequence for buffer mode 0 along with flag

timing. The arrows on the flag timing indicate

when an interrupt will occur if the appropriate in-

terrupt enable bit is set. FLAG0 can cause an inter-

rupt on either edge, which is only shown in the

expanded portion of the figure for clarity.

Buffer Mode 1

In buffer mode 1, eight bytes are allocated for chan-

nel status data and sixteen bytes for auxiliary data

as shown in Figure 5. The user data buffer is the

same for all modes. The channel status buffer, loca-

tions 08H to 0FH, is divided into two sections. The

first four locations always contain the first four

bytes of channel status, identical to mode 0, and are

written once per channel status block. The second

four locations, addresses 0CH to 0FH, provide a

cyclic buffer for the last 20 bytes of channel status

data. The channel status buffer is divided in this

fashion because the first four bytes are the most im-

portant ones; whereas, the last 20 bytes are often

not used (except for byte 23, CRC).

FLAG1 and FLAG2 can be used to monitor this

buffer as shown in Figure 13. FLAG1 is set high

when CS byte 1, location 09H, is written and is tog-

gled when every other byte is written. FLAG2 is set

high after CS byte 23 is written and set low after CS

byte 3, location 0BH, is written. FLAG2 deter-

mines whether the channel status pointer is writing

to the first four-byte section of the channel status

buffer or the second four-byte section, while

FLAG1 indicates which two bytes of the section

are free to update.

The auxiliary data buffer, locations 10H to 1FH, is

written to in a cyclic manner similar to the other

buffers. Four auxiliary data bits are received per

audio sample (sub-frame) and, since the auxiliary

data is four times larger than the user data, the aux-

iliary data buffer on the CS8413 is four times larger

allowing FLAG0 to be used to monitor both.

FLAG0

FLAG1

FLAG2

(384 Audio Samples)

(Expanded)

Block

0B 0C

1F 08

C.S. Address

234

678

10 11 12 13 14 15 16 17 18 19 20 21 22 23 0

C.S. Byte

FLAG0

C.S. Addr.

User Addr.

(Addresses are in Hex)

Figure 12. CS8413 Buffer Memory Write Sequence - MODE 0

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