Data Buffer And Peripheral Hardware - NEC mPD17120 Subseries User Manual

10.2.1 Data Buffer and Peripheral Hardware

Table 10-1 shows data transfer with peripheral hardware using the data buffer.
Each unit of peripheral hardware has an individual address (called its peripheral address). By using this peripheral
address and the dedicated instructions GET and PUT, data can be transferred between each unit of peripheral
hardware and the data buffer.
GET DBF, p : Read the data in the peripheral hardware address specified by p into the data buffer (DBF).
PUT p, DBF: Write the data in the data buffer to the peripheral hardware address specified by p.
There are three types of peripheral hardware units: read/write (PUT/GET), write-only (PUT) and read-only (GET).
The following describes what happens when a GET instruction is used with write-only hardware (PUT only) and
when a PUT instruction is used with read-only hardware (GET only).
• Reading (GET) from write-only (PUT only) peripheral hardware will yield an unpredictable value.
• Writing (PUT) to read-only (GET only) peripheral hardware has no effect (regarded as a NOP instruction).
(1) Peripheral hardware with input/output in 8-bit units
Peripheral
Address
01H
02H
03H
(2) Peripheral hardware with input/output in 16-bit units
Peripheral
Address
40H
CHAPTER 10 DATA BUFFER (DBF)
Table 10-1. Peripheral Hardware
Name Peripheral Hardware
SIOSFR Shift register
TMC Timer count register
TMM Timer modulo register
Name Peripheral Hardware
AR Address register
Direction of Data
Effective Bit
Length
PUT GET
8 bits
×
8 bits
×
8 bits
Direction of Data
Effective Bit
Length
PUT GET
10 bits
81