RSC4128 datasheet(15/49 Pages) ETC

15 / 49 page

Data Sheet

RSC-4128

P/N 80-0206-J

One may also interface to serial memory devices for storage and retrieval of speech data, by using the serial

drivers for ROM, Flash, EEPROM, etc. provided in the Sensory Speech 7 Technology Library. The serial memory

option is useful for applications of the RSC4128 packaged in a 64LQFP (which lacks the external parallel bus) for

which speech or music data exceed the storage capacity of on chip ROM. Using serial ROM, Flash or EEPROM

may result in a simpler, smaller PCB layout and lower overall system cost. The specific I/O used by the serial

interface are configurable. (See the “Sensory Speech 7 Technology Library Manual” for more information). An

example of the optional use of external serial Flash is provided in Reference Schematic 1-1.

Constant/Code Space

When reading, Constant/Code Space can be either internal to the chip or external. Typical uses of this space are

for code storage, and SI recognition set and/or compressed speech constant data storage. When the –XM input

pin is held low, Constant/Code Space is external to the chip when reading and –RDR is the read strobe. When the

–XM pin is high, Constant/Code Space reads are always internal to the chip, and are limited to the physical size of

the internal ROM.

When writing, –WRC is the write strobe regardless of the state of the –XM pin. Writing to Constant/Code Space

requires the MOVC instruction, which is limited to the first 128KBytes of Constant/Code Space.

When reading Constant/Code Space, an application can access up to 1MByte. However, only the first 128KBytes

can be used by the processor for program instructions (Code). The MOVC instruction can only read these first

128KBytes. These first 128KBytes are partitioned into 64Kbyte banks, called Code Bank 0 and Code Bank 1.

(NOTE: Code using both banks up to 128KBytes must provide “mirror” code in both banks for routines such as

Interrupt Service, etc, with protocols to track bank identity.) The MOVX instruction can read the full 1Mbyte.

However, the MOVC is more efficient for reading Constants within the current Code Bank.

The entire 1MByte of Constant/Code Space can be read with the following conditions.

The upper addresses

A[19:16] are generated from Bits[3:0] of Extended Addressing Register (register D2):

1) The MOVX instruction is used to read and Bit 4 (“rw”) of Extended Addressing

The first 128KBytes (addresses 00000H-1FFFFH; Code Banks 0 & 1) can be accessed in two additional ways. For

these two cases, addresses A[19:17] are forced to zero by the RSC4x, and A[16] is generated from Bit 5 (“cb1”) of

the Extended Addressing Register. A “0” in “cb1” selects Code Bank 0 and a “1” selects Code Bank 1:

2) The processor fetches instructions from the active Code Bank.

3) The MOVC instruction is used to read from or write to the active Code Bank.

Data Space

Data Space is always external to the chip and can be up to 1MByte. Typical uses of this space are for storage of

SD recognition template data and/or recorded audio data, and frequently the data is volatile. –RDF is the read

strobe and –WRD is the write strobe. A special bit in the Extended Addressing Register must be set high to allow

the processor to read from the data space using the MOVX instruction. When the “rw” bit (Bit 4 of Register D2) is

set, the MOVX instruction reads from the Data Space.

When writing to Data Space, the MOVX instruction generates a –WRD strobe, regardless of the state of the “rw” bit.

Data space can be accessed in two ways. For both cases, upper addresses A[19:16] are generated from bits [3:0]

of Extended Addressing Register:

1) The MOVX instruction is used to read and bit 4 (“RW”) of Extended

Addressing Register (register D2) is programmed to “1”.

2) The MOVX instruction is used to write.

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