msm80c85ahrs Oki Semiconductor, msm80c85ahrs Datasheet - Page 6

• Manufacturer Part Number: msm80c85ahrs
• Description: 8-bit Cmos Microprocessor
• Manufacturer: Oki Semiconductor

¡ Semiconductor
FUNCTIONAL DESCRIPTION
The MSM80C85AH is a complete 8-bit parallel central processor. It is designed with silicon gate
C-MOS technology and requires a single +5 volt supply. Its basic clock speed is 5 MHz, thus
improving on the present MSM80C85A's performance with higher system speed and power
down mode. Also it is designed to fit into a minimum system of two IC's: The CPU
(MSM80C85AH), and a RAM/IO (MSM81C55-5)
The MSM80C85AH has twelve addressable 8-bit register pairs. Six others can be used
interchangeably as 8-bit registers or 16-bit register pairs. The MSM80C85AH register set is as
follows:
The MSM80C85AH uses a multiplexed Data Bus. The address is spilt between the higher 8-bit
Address Bus and the lower 8-bit Address/Data Bus. During the first T state (clock cycle) of a
machine cycle the low order address is sent out on the Address/Data Bus. These lower 8-bits
may be latched externally by the Address Latch Enable signal (ALE). During the rest of the
machine cycle the data bus is used for mamory or I/O data.
The MSM80C85AH provides RD, WR, S
Acknowledge signal (INTA) is also provided. Hold and all Interrupts are synchronized with
the processor's internal clock. The MSM80C85AH also provides Serial Input Data (SID) and
Serial Output Data (SOD) lines for a simple serial interface.
In addition to these features, the MSM80C85AH has three maskable, vector interrupt pins, one
nonmaskable TRAP interrupt and power down mode with HALT and HOLD.
INTERRUPT AND SERIAL I/O
The MSM80C85AH has 5 interrupt inputs: INTR, RST 5.5 RST 6.5, RST 7.5, and TRAP. INTR is
identical in function to the 8080A INT. Each of the three RESTART inputs, 5.5, 6.5, and 7.5, has
a programmable mask. TRAP is also a RESTART interrupt but it is nonmaskable.
The three maskable interrupts cause the internal execution of RESTART ( saving the program
counter in the stack branching to the RESTART address) it the interrupts are enable and if the
interrupt mask is not set. The nonmaskable TRAP causes the internal execution of a RESTART
vector independent of the state of the interrupt enable or masks. (See Table 1.)
There are two different types of inputs in the restart interrupt. RST 5.5 and RST 6.5 are high
level-sensitive like INTR (and INT on the 8080A) and are recognized with the same timing as
INTR. RST 7.5 is rising edge-sensitive.
ACC or A
PC
BC, DE, HL
SP
Flags or F
Mnemonic
Accumulator
Program Counter
General-Purpose Registers; data pointer (HL)
Stack Pointer
Flag Register
Register
0
, S
1
, and IO/M signals for bus control. An Interrupt
8-bits
16-bit address
8-bit ¥ 6 or 16-bits ¥ 3
16-bit address
5 flags (8-bit space)
MSM80C85AHRS/GS/JS
Contents
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